Wireless communication device

ABSTRACT

There is provided a wireless communication device that includes: a receiving unit that receives a first transmission frame via a receiving antenna, the first transmission frame being a MAC frame transmitted from a communication partner; a response-frame generating unit that generates a first response frame indicating reception of the first transmission frame, based on the first transmission frame received via the receiving antenna; a transmitting unit that transmits the generated first response frame via a transmitting antenna; a determining unit that determines whether or not the same first transmission frame is retransmitted from the communication partner; and an antenna control unit that changes a beam pattern of the transmitting antenna, when the same first transmission frame is retransmitted from the communication partner.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. national stage application of PCTInternational Application No. PCT/JP2014/003032 filed on Jun. 6, 2014,and claims the benefit of foreign priority to Japanese patentapplication 2013-126060 filed on Jun. 14, 2013, the contents all ofwhich are incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a wireless communication device thatswitches a beam pattern of an antenna in wireless communication.

BACKGROUND ART

Wireless LANs (Local Area Networks) defined in, for example, the IEEE(The Institute of Electrical and Electronics Engineers, Inc.) 802.11(for example, IEEE802.11a or IEEE802.11b) communication standard havebeen known for wireless communication for realizing high-speed datatransmission.

Nowadays, with the increasing functionality of digital equipment,digital equipment including wireless communication devices that can usewireless LANs has been in widespread use. Digital equipment can transmita large amount of data (for example, HD (High-Definition) video data) toother digital equipment, for example, by causing wireless communicationdevices to directly communicate with each other without the involvementof an access point.

As a communication method for causing wireless communication devices todirectly communicate with each other, for example, wirelesscommunication using 60 [GHz] millimeter waves has attracted attention.Millimeter wave communication uses a broader band than conventionalwireless LAN communication and thus enables high-speed wirelesscommunications, for example, at 1 [Gbps] or higher, when a range wheremillimeter wave communication is allowed is effectively utilized.However, radio waves in the 60 [GHz] millimeter wave band have shortwavelengths and have a strong characteristic of traveling straight, andare thus susceptible to changes in a radio-wave propagation environment(in the communication environment).

For example, when a human crosses or an obstruction exists between awireless communication device that transmits data and a wirelesscommunication device that receives the data or when the hand of a humanwho holds either of the wireless communication devices moves or rotates,the communication environment changes, and the quality of communicationdeteriorates. Hereinafter, a wireless communication device thattransmits data is referred to as a “data-transmitting wirelesscommunication device”, and a wireless communication device that receivesdata is referred to as a “data-receiving wireless communication device”.Also, the data-transmitting wireless communication device has aconfiguration including a wireless transmitting unit and a wirelessreceiving unit, and the data-receiving wireless communication device hasa configuration including a wireless transmitting unit and a wirelessreceiving unit.

Accordingly, in millimeter wave communication, beamforming is used toset, for example, a beam pattern that suits one of the directivities ofa transmitting antenna and a receiving antenna or a beam pattern thatsuits both of the directivities of the transmitting antenna and thereceiving antenna. The beam pattern of each antenna is set for a singlecommunication partner or is set so that it is appropriate for aplurality of communication partners, although this is not optimum.

In wireless communication devices that use the millimeter wave band toperform wireless communication, the transmitting antenna and thereceiving antenna may be used separately, taking the amount of signalattenuation into account, and different beam patterns may be set for thetransmitting antenna and the receiving antenna. For example, thereceiving antenna is set to be omnidirectional, and a beam patternhaving a main beam formed in a particular direction is set for thetransmitting antenna.

Also, communication protocols in millimeter wave communication involve aprocess (a procedure) for determining the beam pattern of thetransmitting antenna or the receiving antenna. For example, PatentLiterature 1 is known as prior art for determining the beam pattern ofan antenna in millimeter wave communication.

In Patent Literature 1, each time a data-transmitting wirelesscommunication device transmits a transmission frame, it starts a timerand counts the number of transmissions (the number of retransmissions)of a transmission frame (a data frame). When the data-transmittingwireless communication device retransmits a data frame because aresponse with an Ack frame is not returned from a data-receivingwireless communication device, the data-transmitting wirelesscommunication device changes the beam pattern of the transmittingantenna to another beam pattern, when the count value of the timer orthe number of retransmissions of the transmission frame reaches acertain value.

CITATION LIST Patent Literature

PTL 1: U.S. Pat. No. 7,652,624

SUMMARY OF INVENTION Technical Problem

The present inventor has studied a wireless communication device thatswitches the beam pattern of an antenna in wireless communication.However, Patent Literature 1 noted above has a problem in that there arecases in which the beam pattern of a transmitting antenna is changedeven when the change is not necessary, in a data-transmitting wirelesscommunication device, although a transmission frame is received by adata-receiving wireless communication device because thedata-transmitting wireless communication device changes the beam patternof the transmitting antenna a under certain condition.

In order to overcome the above-described problem, the present disclosureprovides a wireless communication device that avoids an unnecessarychange of the beam pattern of an antenna and that suppressesdeterioration of the quality of communication.

Solution to Problem

The present disclosure provides a wireless communication device thatincludes: a receiving unit that receives a first transmission frame viaa receiving antenna, the first transmission frame being a MAC frametransmitted from a communication partner; a response-frame generatingunit that generates a first response frame indicating reception of thefirst transmission frame, based on the first transmission frame receivedvia the receiving antenna; a transmitting unit that transmits thegenerated first response frame via a transmitting antenna; a determiningunit that determines whether or not the same first transmission frame isretransmitted from the communication partner; and an antenna controlunit that changes a beam pattern of the transmitting antenna, when thesame first transmission frame is retransmitted from the communicationpartner.

Advantageous Effects of Invention

According to the present disclosure, it is possible to avoid anunnecessary change of the beam pattern of an antenna and it is possibleto suppress deterioration of the quality of communication.

FIG. 1A is a diagram showing an omnidirectional beam pattern;

FIG. 1B is a diagram showing a quasi-omnidirectional beam pattern;

FIG. 1C is a diagram showing a beam pattern having a plurality of (forexample, three) directivities and having a main beam formed in one ofdirections;

FIG. 1D is an explanatory diagram of a communication example when thebeam pattern having directivity in a specific direction is set for atransmitting antenna of a data-transmitting wireless communicationdevice, and the quasi-omnidirectional beam pattern is set for areceiving antenna of a data-receiving wireless communication device;

FIG. 2 is a block diagram showing one example of an internal basicconfiguration of a wireless communication device in each embodiment;

FIG. 3A is a block diagram showing one example of an internalconfiguration of a wireless communication device that uses aretransmission-bit determining unit as one example of a determining unitin the wireless communication device shown in FIG. 2;

FIG. 3B is a block diagram showing one example of an internalconfiguration of a wireless communication device that uses an SNdetermining unit as one example of the determining unit in the wirelesscommunication device shown in FIG. 2;

FIG. 4A is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna for an Ack frame inresponse to a MAC frame (for example, a data frame) received by adata-receiving wireless communication device in a first embodiment;

FIG. 4B is a flowchart illustrating another example of the procedure forsetting the beam pattern of the transmitting antenna for an Ack frame inresponse to a MAC frame (for example, a data frame) received by thedata-receiving wireless communication device in the first embodiment;

FIG. 5A is a sequence diagram showing one example of signaling in whicha sequence number SN is changed upon reception of an Ack frame, thesignaling being performed by the data-transmitting wirelesscommunication device and the data-receiving wireless communicationdevice in the first embodiment;

FIG. 5B is a sequence diagram showing one example of signaling in whicha sequence number SN is changed upon reaching of an upper limit of thenumber of retransmissions, the signaling being performed by thedata-transmitting wireless communication device and the data-receivingwireless communication device in the first embodiment;

FIG. 6A is a sequence diagram showing another example of signaling inwhich a sequence number SN is changed upon reception of an Ack frame,the signaling being performed by the data-transmitting wirelesscommunication device and the data-receiving wireless communicationdevice in the first embodiment;

FIG. 6B is a sequence diagram showing another example of signaling inwhich a sequence number SN is changed upon reaching of the upper limitof the number of retransmissions, the signaling being performed by thedata-transmitting wireless communication device and the data-receivingwireless communication device in the first embodiment;

FIG. 7A is an explanatory diagram showing an example in whichtransmission of a data frame from the data-transmitting wirelesscommunication device to the data-receiving wireless communication devicehas succeeded after the beam pattern was determined;

FIG. 7B is an explanatory diagram showing an example in whichtransmission of an Ack frame from the data-receiving wirelesscommunication device to the data-transmitting wireless communicationdevice has succeeded after the beam pattern was determined;

FIG. 7C is an explanatory diagram showing an example in whichtransmission of a data frame from the data-transmitting wirelesscommunication device to the data-receiving wireless communication devicehas succeeded after the data-receiving wireless communication device wasrotated;

FIG. 7D is an explanatory diagram showing an example in whichtransmission of an Ack frame from the data-receiving wirelesscommunication device to the data-transmitting wireless communicationdevice has failed after the data-receiving wireless communication devicewas rotated;

FIG. 7E is an explanatory diagram showing an example in whichtransmission of a data frame from the data-transmitting wirelesscommunication device to the data-receiving wireless communication devicehas succeeded after the data-receiving wireless communication device wasrotated;

FIG. 7F is an explanatory diagram showing an example in whichtransmission of an Ack frame from the data-receiving wirelesscommunication device to the data-transmitting wireless communicationdevice has succeeded after the data-receiving wireless communicationdevice was rotated and the beam pattern of the transmitting antenna waschanged;

FIG. 8A is a flowchart illustrating one example of an operationprocedure for the data-receiving wireless communication device in thefirst embodiment to transmit a data frame by using the beam pattern ofthe transmitting antenna for transmitting an Ack frame;

FIG. 8B is a sequence diagram showing one example of signaling for thedata-receiving wireless communication device shown in FIG. 8A totransmit a data frame by using the beam pattern of the transmittingantenna for transmitting an Ack frame;

FIG. 9 is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna for transmitting anAck frame in response to a data frame received by the data-receivingwireless communication device in a first modification of the firstembodiment;

FIG. 10 is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna for transmitting anAck frame in response to a data frame received by the data-receivingwireless communication device in a second modification of the firstembodiment and the beam pattern of the receiving antenna for receiving adata frame next time;

FIG. 11 is a sequence diagram showing one example of signaling regardingtransmission of an aggregation data frame, the signaling being performedby a data-transmitting wireless communication device and adata-receiving wireless communication device in a second embodiment;

FIG. 12 is a flowchart illustrating one example of a procedure forsetting the beam pattern of a transmitting antenna for transmitting ablock Ack frame corresponding to an aggregation data frame received bythe data-receiving wireless communication device in the secondembodiment;

FIG. 13 is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna for transmitting anAck frame corresponding to a MAC frame received by the data-receivingwireless communication device in a third modification of the firstembodiment;

FIG. 14A is a diagram showing one example of the format of aconventional MAC frame.

FIG. 14B is a diagram showing one example of the format of aconventional sequence control field;

FIG. 14C is a diagram showing one example of the format of aconventional frame control field;

FIG. 14D is a diagram showing one example of the format of aconventional Ack frame;

FIG. 15A is a sequence diagram showing the concept of signaling of asingle data frame between a conventional data-transmitting wirelesscommunication device and a data-receiving wireless communication device;

FIG. 15B is a sequence diagram showing one example of signaling of asingle data frame between a conventional data-transmitting wirelesscommunication device and a data-receiving wireless communication device;

FIG. 16A is a diagram showing one example of the format of aconventional A-MPDU frame;

FIG. 16B is a diagram showing one example of the format of aconventional A-MPDU sub frame;

FIG. 16C is a diagram showing one example of the format of aconventional block Ack frame;

FIG. 17A is a sequence diagram showing the concept of signaling of atransmission aggregation frame between the conventionaldata-transmitting wireless communication device and the data-receivingwireless communication device;

FIG. 17B is a sequence diagram showing one example of signaling of atransmission aggregation frame between the conventionaldata-transmitting wireless communication device and the data-receivingwireless communication device;

FIG. 17C is a sequence diagram showing another example of signaling of atransmission aggregation frame between the conventionaldata-transmitting wireless communication device and the data-receivingwireless communication device;

FIG. 18A is an explanatory diagram of a transmission cycle including asetting period for setting the beam pattern of an antenna and acommunication period in a conventional millimeter wave communication;

FIG. 18B is an explanatory diagram of a timing at which deterioration ofa communication environment occurs in the transmission period includingthe setting period for setting the beam pattern of the antenna and thecommunication period in the conventional millimeter wave communication;

FIG. 19A is a flowchart illustrating one example of a procedure forsetting the beam pattern of a transmitting antenna for a CTS frame inresponse to a MAC frame (for example, an RTS frame) received by adata-receiving wireless communication device in a fourth modification ofthe first embodiment;

FIG. 19B is a sequence diagram showing one example of signaling in whicha frame type is changed upon reception of a CTS frame, the signalingbeing performed by a data-transmitting wireless communication device andthe data-receiving wireless communication device in the fourthmodification of the first embodiment.

DESCRIPTION OF EMBODIMENTS Background from which Content of EachEmbodiment is Derived

First, before embodiments of a wireless communication device accordingto the present disclosure are described, Patent Literature 1 noted aboveand problems with Patent Literature 1 will be described as thebackground from which content of each embodiment is derived. Adata-transmitting wireless communication device has a configurationincluding a wireless transmitting unit and a wireless receiving unit,and a data-receiving wireless communication device has a configurationincluding a wireless transmitting unit and a wireless receiving unit.Also, a description will be given assuming a case in which thedata-transmitting wireless communication device and the data-receivingwireless communication device have a similar configuration and perform,for example, direct communication.

Communication protocols (for example, IEEE802.11ad) using millimeterwave communication involve a process (a procedure) for determining abeam pattern of a transmitting antenna or a receiving antenna (see FIG.18A). FIG. 18A is an explanatory diagram of transmission cycles TR eachincluding a setting period PH1 for setting the beam pattern of anantenna and a communication period PH2 in conventional millimeter wavecommunication. FIG. 18B is an explanatory diagram of a timing at whichdeterioration of a communication environment occurs in the transmissioncycle TR including the setting period PH1 for setting the beam patternof the antenna and the communication period PH2 in the conventionalmillimeter wave communication.

Each transmission cycle TR shown in FIG. 18A includes the setting periodPH1 (Antenna Training Phase) for setting the beam pattern of the antennain the millimeter wave communication and the actual-communication (datatransaction) period PH2 (Communication Phase). The time spans of thetransmission cycles TR may be the same or may be different from those ofother transmission cycles TR.

In the setting period PH1, the data-transmitting wireless communicationdevice sets a plurality of antenna beam patterns having differentdirectivities and transmits a frame for directivity verification to thedata-receiving wireless communication device, which is a communicationpartner, the frame including information regarding the antenna beampattern. After receiving the frame for directivity verification, thedata-receiving wireless communication device returns, to thedata-transmitting wireless communication device, a response frameincluding information regarding which antenna beam pattern isappropriate and regarding an antenna to be used in the communicationperiod PH2.

On the basis of the response frame returned from the data-receivingwireless communication device, the data-transmitting wirelesscommunication device sets a transmitting-antenna beam pattern for acommunication with the data-receiving wireless communication device. Asa result, the transmitting-antenna beam pattern for the communicationpartner of the data-transmitting wireless communication device is set inthe setting period PH1.

However, in the transmission cycle TR shown in FIG. 18A, thecommunication period PH2 becomes short in accordance with the length ofthe setting period PH1, compared with a transmission cycle in which thesetting period PH1 is not set. Since the time span of the transmissioncycle TR does not change, the communication period PH2 is reduced, andthe available channel access time in the communication period PH2 isreduced, as the setting period PH1 increases.

Also, there is a problem in that, when a time (Duration) passes fromstart of the communication period PH2 after the setting period PH1, anda change occurs in the communication environment (see FIG. 18B), thebeam pattern of the transmitting antenna for the communication partnerof the data-transmitting wireless communication device needs to be setagain in the remaining communication period PH2, as in the settingperiod PH1, because of the characteristics of millimeter waves.

In Patent Literature 1, to address the above-described problem, thedata-transmitting wireless communication device reduces the number ofsettings of the beam pattern of the transmitting antenna and selects anappropriate antenna beam pattern during communication.

However, in Patent Literature 1, as to the cause for why thedata-transmitting wireless communication device retransmits a data framewhen an Ack frame has not arrived at the data-transmitting wirelesscommunication device, there are the following two possible causes. Afirst cause is a case in which, since a data frame has not arrived atthe data-receiving wireless communication device, the data-receivingwireless communication device has not returned an Ack frame. A secondcause is a case in which, although a data frame has arrived at thedata-receiving wireless communication device, an Ack frame returned fromthe data-receiving wireless communication device has not arrived at thedata-transmitting wireless communication device.

Accordingly, in Patent Literature 1, when the cause for why thedata-transmitting wireless communication device retransmits a data frameis the above-described second cause, even if the beam pattern of thetransmitting antenna of the data-transmitting wireless communicationdevice is appropriate, the data-transmitting wireless communicationdevice changes the beam pattern of the transmitting antenna to anotherbeam pattern to retransmit the data frame. Thus, since thedata-transmitting wireless communication device performs an unnecessarychange of the beam pattern of the transmitting antenna, there is aproblem in that the quality of communication between thedata-transmitting wireless communication device and the data-receivingwireless communication device, which is a communication partner,deteriorates.

Accordingly, in each embodiment below, a description will be given of anexample of a wireless communication device that avoids an unnecessarychange of the beam pattern of an antenna and that suppressesdeterioration of the quality of communication.

Next, before each embodiment of a wireless communication deviceaccording to the present disclosure is described, technical knowledgethat serves as a premise of the content of each embodiment will bedescribed with reference to FIG. 14 to FIG. 17. In the description inFIG. 14 to FIG. 17, for ease of description, a case in which twowireless communication devices perform direct communication is assumed:a wireless communication device at a transmitting end is simply referredto as a “data-transmitting wireless communication device”, and awireless communication device at a receiving end is simply referred toas a “data-receiving wireless communication device” (for example, seeFIG. 15A or FIG. 17A).

FIG. 14A is a diagram showing one example of the format of aconventional MAC frame. FIG. 14B is a diagram showing one example of theformat of a conventional sequence control field. FIG. 14C is a diagramshowing one example of the format of a conventional frame control field.FIG. 14D is a diagram showing one example of the format of aconventional Ack frame. A wireless communication device in a firstembodiment below transmits/receives a MAC frame (for example, a Dataframe) having, for example, the format shown in FIG. 14A.

The MAC frame shown in FIG. 14A includes fields for Frame Control,Duration/ID, Address 1, Address 2, Address 3, Sequence Control, Address4, Qos (Quality of Service) control, HT (High Throughput) control, FrameBody, and FCS (Frame Check Sequence). In the MAC frame, the fields otherthan for the frame body and the FCS constitute a MAC Header.

The sequence control field shown in FIG. 14B includes fields forFragment Number and Sequence Number. The sequence number indicates anidentification number or a transmission order of the MAC frame shown inFIG. 14A. For example, when the sequence number field is 12 bits, thesequence number is an integer value of one of 0 to 4095.

The frame control field shown in FIG. 14C includes fields for ProtocolVersion, Type, Subtype, To DS (Distribution Service), From DS, MoreFragments, Retry, Power Management, More Data, Protected Frame, andOrder. A retry bit indicating whether or not the MAC frame shown in FIG.14A is retransmitted is stored in the retry field. For example, when theretry bit is 1, this indicates that the MAC frame is a retransmitted MACframe, and when the retry bit is 0, this indicates that the MAC frame isa newly transmitted MAC frame.

The Ack frame shown in FIG. 14D includes fields for Frame Control,Duration, RA (Receiver Address, receiving-station address), and FCS. Inthe Ack frame, the fields other than for the FCS constitute a MACHeader.

Wireless communication standards (for example, IEEE802.11) that realizehigh-speed data transmission define a communication protocol for CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) or for timedivision multiplexing communication (SPCA: Service Period ChannelAccess) using centralized control involving wireless band assignment ata wireless base station.

For example, in CSMA/CA, a data-transmitting wireless communicationdevice Dv11 performs carrier sense before transmitting a data frame andstarts transmission of the data frame when no carrier is detected in apredetermined specified time. The data-transmitting wirelesscommunication device Dv11 and a data-receiving wireless communicationdevice Dv12 perform a series of data frame transmission and Ack frameresponse transmission sequences over a certain period called a TXOP(Transmission Opportunity) initiated, for example, by transmission of adata frame (see FIG. 15A).

In CSMA/CA, after determining, through the carrier sense, thattransmission to the data-receiving wireless communication device Dv2 isto be performed, the data-transmitting wireless communication device Dv1uses, for example, the transmitting-antenna beam pattern set and held inthe setting period PH1 shown in FIG. 18A to transmit a data frame to thedata-receiving wireless communication device Dv2.

However, it is difficult for the data-receiving wireless communicationdevice Dv2 to know, in advance, the time at which the data-transmittingwireless communication device Dv1 transmits a data frame. Also, sincethere is also the possibility that a data frame is transmitted fromother data-transmitting wireless communication devices to thedata-receiving wireless communication device Dv2 at a point in time, thedata-receiving wireless communication device Dv2 sets thereceiving-antenna beam pattern to a large range so as to be able toreceive data frames transmitted from the data-transmitting wirelesscommunication device Dv1 and the other data-transmitting wirelesscommunication device (see FIG. 1A or FIG. 1B).

FIG. 15A is a sequence diagram showing the concept of signaling of asingle data frame between a conventional data-transmitting wirelesscommunication device Dv11 and a conventional data-receiving wirelesscommunication device Dv12. When the data-receiving wirelesscommunication device Dv12 properly receives a data frame transmitted bythe data-transmitting wireless communication device Dv11, it makes aresponse with an Ack frame serving as a response frame to thedata-transmitting wireless communication device Dv11 within apredetermined period called a max ack delay.

Upon receiving the Ack frame, the data-transmitting wirelesscommunication device Dv11 determines that the data frame transmitted bythe data-transmitting wireless communication device Dv11 was properlyreceived by the data-receiving wireless communication device Dv12, andwhen the data-transmitting wireless communication device Dv11 does notreceive the Ack frame, it determines that the data frame transmitted bythe data-transmitting wireless communication device Dv11 was notproperly received by the data-receiving wireless communication deviceDv12.

When the data-transmitting wireless communication device Dv11 receivesthe Ack frame, it determines that a next data frame is to betransmitted, increments the sequence number (SN) assigned to each dataframe by 1, and generates a data frame in which the retry bit is set to0. The sequence number is managed in association with an address of thedata-transmitting wireless communication device Dv11 and an address anda TID (Traffic Identifier) of the data-receiving wireless communicationdevice Dv12.

On the other hand, when the data-transmitting wireless communicationdevice Dv11 does not receive an Ack frame, it retransmits the same dataframe. However, the sequence number of the data frame to beretransmitted is not changed, and the retry bit is set to 1 (see FIG.15B).

FIG. 15B is a sequence diagram showing one example of signaling of asingle data frame between the conventional data-transmitting wirelesscommunication device Dv11 and the data-receiving wireless communicationdevice Dv12. When the data-transmitting wireless communication deviceDv11 does not properly receive an Ack frame corresponding to atransmitted data frame, for example, it retransmits the data frame inwhich, for example, the sequence number is held at 1 and the retry bitis set to 1 to the data-receiving wireless communication device Dv12.

When the data-transmitting wireless communication device Dv11 does notproperly receive an Ack frame again after transmitting the data frame inwhich the sequence number is held at 1 and the retry bit is set to 1 tothe data-receiving wireless communication device Dv12, thedata-transmitting wireless communication device Dv11 retransmits thedata frame. Also, the data-transmitting wireless communication deviceDv11 counts the number of retransmissions and does not performretransmissions that exceed a predetermined upper limit number of times.Also, when the data-transmitting wireless communication device Dv11determines that the transmission of a data frame to be retransmittedsucceeds, it resets the counter for the number of retransmissions.

FIG. 16A is a diagram showing one example of the format of aconventional A-MPDU frame. FIG. 16B is a diagram showing one example ofthe format of a conventional A-MPDU subframe. FIG. 16C is a diagramshowing one example of the format of a conventional block Ack frame. Awireless communication device in a second embodiment belowtransmits/receives, for example, an Aggregation frame (A-MPDU: AggregateMedium Access Control Protocol Data Unit) having the format shown inFIG. 16A.

The aggregation frame shown in FIG. 16A includes fields for a pluralityof A-MPDU sub frames. The A-MPDU subframe shown in FIG. 16B includesfields for an MPDU delimiter serving as segmentation information of theA-MPDU subframe, an MPDU that is similar to the MAC frame shown in FIG.14A, and Padding for alignment.

The block Ack frame shown in FIG. 16C includes fields for Frame Control,Duration/ID, RA (Receiver Address) representing a reception-destinationaddress of the block Ack frame, TA (Transmission Address) representing atransmission-source address of the block Ack frame, BA control (BlockAck Control), BA information (Block Ack Information), and FCS. In theblock Ack frame, fields other than for the BA control, the BAinformation, and the FCS constitute a MAC Header.

With the aim of improving the transmission efficiency, a system is alsoknown in which MAC frames having a plurality of sequence numbers aretransmitted/received at the same time through transmission of theaggregation frame (A-MPDU) shown in FIG. 16A and a response using ablock Ack frame indicating the reception of the aggregation frame. Byreturning the block Ack frame, the data-receiving wireless communicationdevice Dv12 can make responses at the same time about properly receiving(Ack) or not properly receiving (Nack (No Acknowledge)) with respect toa plurality of data frames (MPDU) coupled as an aggregation frame (seeFIG. 17A).

FIG. 17A is a sequence diagram showing the concept of signaling of atransmission aggregation frame between the conventionaldata-transmitting wireless communication device and the data-receivingwireless communication device. When the data-receiving wirelesscommunication device Dv12 receives the data frame(s) (MPDU) having someor all of the sequence numbers in the aggregation frame transmitted bythe data-transmitting wireless communication device Dv11, thedata-receiving wireless communication device Dv12 makes a response witha block Ack frame serving as a response frame to the data-transmittingwireless communication device Dv11 within a predetermined period calleda max ack delay.

Upon receiving the block Ack frame, the data-transmitting wirelesscommunication device Dv11 determines that the data frame(s) (MPDU)having some or all of the sequence numbers in the aggregation frametransmitted by the data-transmitting wireless communication device Dv11was received by the data-receiving wireless communication device Dv12,and when the data-transmitting wireless communication device Dv11 doesnot receive the block Ack frame, it determines that the aggregationframe transmitted by the data-transmitting wireless communication deviceDv11 was not properly received by the data-receiving wirelesscommunication device Dv12.

When the data-transmitting wireless communication device Dv11successfully receives the block Ack frame, it analyzes the contents ofthe block Ack frame and determines the sequence number of each dataframe (MPDU) that was properly received and the sequence number of eachdata frame (MPDU) that was not properly received. In accordance with aresult of the determination, the data-transmitting wirelesscommunication device Dv11 generates an aggregation frame including thesequence number of each data frame (MPDU) that was not properly receivedand the sequence number of each data frame (MPDU) that is to be newlytransmitted (see FIG. 17C).

On the other hand, when the data-transmitting wireless communicationdevice Dv11 does not receive the block Ack frame, it retransmits thesame aggregation frame (FIG. 17B).

FIG. 17B is a sequence diagram showing one example of signaling of atransmission aggregation frame between the conventionaldata-transmitting wireless communication device and the data-receivingwireless communication device. FIG. 17C is a sequence diagram showinganother example of signaling of a transmission aggregation frame betweenthe conventional data-transmitting wireless communication device and thedata-receiving wireless communication device.

Next, each embodiment of a wireless communication device according tothe present disclosure will be described with reference to the drawings.The wireless communication device in each embodiment wirelesslycommunicates with a wireless communication device, which is acommunication partner, for example, by using a millimeter wave (forexample, 60 [GHz]) defined by the IEEE802.11ad communication standard.Also, in each embodiment below, a description will be given assuming acase in which a wireless communication device that transmits data(hereinafter simply referred to as a “data-transmitting wirelesscommunication device”) in each embodiment and a wireless communicationdevice that receives data (hereinafter simply referred to as a“data-receiving wireless communication device”) in each embodiment havea similar configuration and perform, for example, direct communication.Also, the data-transmitting wireless communication device has aconfiguration including a wireless transmitting unit and a wirelessreceiving unit, and the data-receiving wireless communication device hasa configuration including a wireless transmitting unit and a wirelessreceiving unit.

(Beam Pattern of Antenna)

First, formation of the beam pattern of a transmitting antenna or areceiving antenna of the wireless communication device in eachembodiment will be described with reference to FIG. 1A to FIG. 1D.

FIG. 1A is a diagram showing an omnidirectional beam pattern PA1. FIG.1B is a diagram showing a quasi-omnidirectional beam pattern PA2. FIG.4C is a beam pattern PA3 having a plurality of (for example, three)directivities and having a main beam formed in one of the directions.FIG. 1D is an explanatory diagram of a communication example of a casein which the beam pattern PA3 having directivity in a specific directionis set for the transmitting antenna of the data-transmitting wirelesscommunication device Dv1 and the quasi-omnidirectional beam pattern PA2is set for the receiving antenna of the data-receiving wirelesscommunication device Dv2.

For transmitting or receiving a MAC frame or an aggregation frame, forexample, the data-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 set the beam pattern ofeach transmitting antenna or receiving antenna to the omnidirectional(omni) beam pattern PA1 (see FIG. 1A) or the quasi-omnidirectional(quasi-omni) beam pattern PA2.

A beam pattern directivity having a wide beam width of thedata-transmitting wireless communication device Dv1 or thedata-receiving wireless communication device Dv2 is hereinafter referredto as “quasi-omnidirectivity (quasi-omni)”. Accordingly, in thequasi-omnidirectional beam pattern PA2, the arrival distance orreception distance of frames is small, but the beam width is large,compared with the beam pattern PA3 having the directivity in thespecific direction shown in FIG. 1C.

Also, for transmitting or receiving a MAC frame or an aggregation frame,the data-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 can also set the beampattern of each transmitting antenna or receiving antenna to the beampattern PA3 having the main beam formed in a specific direction (seeFIG. 1C).

When the transmitting antenna of the data-transmitting wirelesscommunication device Dv1 is set to the beam pattern PA3 having the mainbeam formed in a specific direction, and the receiving antenna of thedata-receiving wireless communication device Dv2 is set to thequasi-omnidirectional beam pattern PA2, for example, as shown in FIG.1D, a MAC frame or an aggregation frame transmitted by thedata-transmitting wireless communication device Dv1 is received by thedata-receiving wireless communication device Dv2.

FIRST EMBODIMENT

In a first embodiment, a description will be given assuming a case inwhich, for example, the data-transmitting wireless communication deviceDv1 transmits a MAC frame shown in FIG. 14A, and the data-receivingwireless communication device Dv2 makes a response with an Ack frameindicating that a MAC frame is received.

FIG. 2 is a block diagram showing one example of an internal basicconfiguration of a wireless communication device 1 in each embodiment.The wireless communication device 1 shown in FIG. 2 has a configurationaimed for, for example, a data-receiving wireless communication devicethat receives a MAC frame transmitted from another wirelesscommunication device (for example, the data-transmitting wirelesscommunication device Dv1 or the data-receiving wireless communicationdevice Dv2), which is a communication partner, and that makes a responsewith an Ack frame indicating that a MAC frame is received.

Specifically, the wireless communication device 1 shown in FIG. 2includes a wireless receiving unit 11 to which a receiving antenna ARXis connected, a response-needed/not-needed determining unit 12, aresponse-frame generating unit 13, a wireless transmitting unit 14 towhich a transmitting antenna ATX is connected, a determining unit 15,and an antenna control unit 16.

Before the period PH2 (see FIG. 18A) of communication with the otherwireless communication device (for example, the data-transmittingwireless communication device Dv1 or the data-receiving wirelesscommunication device Dv2), which is a communication partner, is started,a beam pattern is set for the receiving antenna ARX in the settingperiod PH1 shown in FIG. 18A. That is, in response to an antenna controlsignal output by the antenna control unit 16, a beam pattern having apredetermined directivity is set for the receiving antenna ARX by abeamforming technique and is held.

Through use of the held beam pattern, the receiving antenna ARX receivesa MAC frame (for example, a data frame) or an Ack frame transmitted bythe other wireless communication device (for example, thedata-transmitting wireless communication device Dv1 or thedata-receiving wireless communication device Dv2) and outputs the MACframe or Ack frame to the wireless receiving unit 11.

Also, in the period PH2 of communication with the other wirelesscommunication device (for example, the data-transmitting wirelesscommunication device Dv1 or the data-receiving wireless communicationdevice Dv2), the beam pattern of the receiving antenna ARX is alsochanged by the beamforming technique and is held in accordance with anantenna control signal output by the antenna control unit 16.

Before the period PH2 (see FIG. 18A) of communication with the otherwireless communication device (for example, the data-transmittingwireless communication device Dv1 or the data-receiving wirelesscommunication device Dv2), which is a communication partner, is started,a beam pattern is set for the transmitting antenna ATX in the settingperiod PH1 shown in FIG. 18A. That is, a beam pattern having apredetermined directivity is set for the transmitting antenna ATX by thebeamforming technique and is held in accordance with an antenna controlsignal output by the antenna control unit 16.

Through use of the held beam pattern, the transmitting antenna ATXtransmits a MAC frame (for example, a data frame) or an Ack frametransmitted by the other wireless communication device (for example, thedata-transmitting wireless communication device Dv1 or thedata-receiving wireless communication device Dv2).

Also, in the period PH2 of communication with the other wirelesscommunication device (for example, the data-transmitting wirelesscommunication device Dv1 or the data-receiving wireless communicationdevice Dv2), the beam pattern of the transmitting antenna ATX is alsochanged by the beamforming technique and is held in accordance with anantenna control signal output by the antenna control unit 16.

The wireless receiving unit 11 converts signals in the MAC frame or Ackframe in a carrier frequency band, the frame being received by thereceiving antenna ARX, into baseband signals and demodulates thebaseband signals. When a destination address (for example, see theAddress 1 field shown in FIG. 14A) of the demodulated MAC frame or areceiving-station address (for example, see the RA (Receiver Address)field shown in FIG. 14D) of the demodulated Ack frame matches a MACaddress of the local station, the wireless receiving unit 11 determinesthat the MAC frame or the Ack frame is a frame addressed to the localstation.

After determining that the MAC frame or the Ack frame is a frameaddressed to the local station, the wireless receiving unit 11determines whether or not a value computed based on the contents of theMAC frame or the Ack frame and the value of the FCS match each other.When the wireless receiving unit 11 determines that the value computedbased on the contents of the MAC frame or the Ack frame and the value ofthe FCS (for example, CRC32 (Cyclic Redundancy Code 32)) match eachother, the wireless receiving unit 11 determines that the MAC frame orthe Ack frame has been properly received.

After determining that the MAC frame or the Ack frame has been properlyreceived, the wireless receiving unit 11 outputs the MAC frame or theAck frame to the response-needed/not-needed determining unit 12 and thedetermining unit 15.

Also, when the wireless receiving unit 11 receives the MAC frame or theAck frame but determines that it is not a MAC frame or Ack frameaddressed to the local station or that the value computed based on thecontents of the MAC frame or the Ack frame and the value of the FCS dono match each other, the wireless receiving unit 11 determines that aMAC frame or an Ack frame has not been properly received. The wirelessreceiving unit 11 discards the MAC frame or Ack frame and waits until anext reception.

On the basis of a frame type (for example, see the Type or the Subtypefield shown in FIG. 14C or a response type (for example, see the QoScontrol field shown in FIG. 14A) of the MAC frame demodulated by thewireless receiving unit 11, the response-needed/not-needed determiningunit 12 determines whether or not a response with an Ack frameindicating that the MAC frame is received is needed.

The response-needed/not-needed determining unit 12 outputs the MAC framedemodulated by the wireless receiving unit 11 to an upper layer (notshown) of the wireless communication device 1 and outputs, to theresponse-frame generating unit 13, the determining unit 15, and theantenna control unit 16, a result of the determination as to whether ornot a response with an Ack frame is needed. When theresponse-needed/not-needed determining unit 12 determines that aresponse with an Ack frame is not needed, the wireless communicationdevice 1 does not make a response with an Ack frame indicating that theMAC frame has been received.

When the response-needed/not-needed determining unit 12 determines thata response with an Ack frame is needed, the response-frame generatingunit 13 generates an Ack frame indicating that the MAC frame has beenreceived and outputs the Ack frame to the wireless transmitting unit 14.

The wireless transmitting unit 14 converts the Ack frame generated bythe response-frame generating unit 13 into signals in a predeterminedcarrier frequency band and transmits the signals via the transmittingantenna ATX. When a predetermined specified time (for example, SIFS:Short Inter Frame Space in IEEE802.11) passes after a point in time whena MAC frame is received by the receiving antenna ARX, the wirelesstransmitting unit 14 makes a response with an Ack frame. Thus, thewireless communication device 1 can inform the communication partnerthat the MAC frame transmitted from the communication partner has beenproperly received.

When the response-needed/not-needed determining unit 12 determines thata response with an Ack frame is needed, the determining unit 15determines whether or not the same MAC frame has been retransmitted fromthe communication partner, on the basis of the MAC frame demodulated bythe wireless receiving unit 11. The determining unit 15 is configuredusing, for example, a retransmission-bit determining unit 15A in awireless communication device 1A shown in FIG. 3A or an SN determiningunit 15B in a wireless communication device 1B shown in FIG. 3B.

FIG. 3A is a block diagram showing one example of an internalconfiguration of the wireless communication device 1A that uses theretransmission-bit determining unit 15A as one example of thedetermining unit 15 in the wireless communication device 1 shown in FIG.2. FIG. 3B is a block diagram showing one example of an internalconfiguration of the wireless communication device 1B that uses the SNdetermining unit 15B as one example of the determining unit 15 in thewireless communication device 1 shown in FIG. 2.

The retransmission-bit determining unit 15A in the wirelesscommunication device 1A determines whether the retry bit in the retryfield (for example, the “retry” shown in FIG. 14A) in a MAC framedemodulated by a wireless receiving unit 11 is 1 indicatingretransmission or 0 indicating new transmission, and outputs a result ofthe determination to a transmitting-antenna control unit 16T in anantenna control unit 16.

In this case, since the data-receiving wireless communication device Dv2has properly received a MAC frame, it can be determined that beampatterns set in the setting period PH1 are effective, specifically thebeam patterns of the transmitting antenna ATX of the data-transmittingwireless communication device Dv1 and the receiving antenna ARX of thedata-receiving wireless communication device Dv2.

In contrast, since the retry bit in the received MAC frame is 1, thismeans that the MAC frame was retransmitted one or more times from thedata-transmitting wireless communication device Dv1, which is acommunication partner, before the data-receiving wireless communicationdevice Dv2 has properly received the MAC frame, and the data-receivingwireless communication device Dv2 returned an Ack frame indicatingproper reception of a MAC frame but the returned Ack frame has not beenproperly received by the data-transmitting wireless communication deviceDv1, which is a communication partner.

In this case, the beam pattern of the transmitting antenna ATX of thedata-receiving wireless communication device Dv2 used for returning theAck frame and the beam pattern of the receiving antenna ARX of thedata-transmitting wireless communication device Dv1, the beam patternsbeing set in the setting period PH1, are thought to be not appropriate.

The SN determining unit 15B in the wireless communication device 1Bdetermines whether or not the sequence number in the sequence controlfield in a MAC frame demodulated by the wireless receiving unit 11 andthe sequence number in the sequence control field in a MAC framepreviously received and demodulated by the wireless receiving unit 11are the same and outputs a result of the determination to thetransmitting-antenna control unit 16T in the antenna control unit 16.

That is, when a MAC frame having the same sequence number has beenreceived a plurality of times before the count of a finite number ofsequence numbers reaches its full count, this means that thedata-receiving wireless communication device Dv2 has redundantlyreceived the same MAC frame, that is, the same MAC frame has beenretransmitted from the data-transmitting wireless communication deviceDv1, which is a communication partner.

Thus, it can be determined that the beam patterns set in the settingperiod PH1 are effective for the beam patterns of the transmittingantenna ATX of the data-transmitting wireless communication device Dv1and the antenna ARX of the data-receiving wireless communication deviceDv2.

In contrast, the beam patterns of the transmitting antenna ATX of thedata-receiving wireless communication device Dv2 used for returning theAck frame and the receiving antenna ARX of the data-transmittingwireless communication device Dv1, the beam patterns being set in thesetting period PH1, are thought to be not appropriate.

The SN determining unit 15B manages the sequence numbers in associationwith each of all or some pairs each consisting of a destination address(for example, see address 1 in FIG. 14A) or a receiving-station address(for example, see RA shown in FIG. 14D) and a TID (Traffic Identifier)representing an identifier of a logical link.

Also, the SN determining unit 15B stores the sequence numbers of MACframes previously received by the wireless communication device 1B.Hereinafter, for ease of description of the present embodiment, thesequence number of a MAC frame previously received and stored by the SNdetermining unit 15B is simply referred to as a “stored SN”, and thesequence number of a MAC frame received via the receiving antenna ARX issimply referred to as a “received SN”.

The antenna control unit 16 includes the transmitting-antenna controlunit 16T and a receiving-antenna control unit 16R. Although the antennacontrol unit 16 shown in FIG. 2 will be described as including thetransmitting-antenna control unit 16T and the receiving-antenna controlunit 16R shown in FIG. 3A or FIG. 3B, the antenna control unit 16 mayalso control the beam patterns of the transmitting antenna ATX and thereceiving antenna ARX.

Before starting the period PH2 (see FIG. 18A) of communication with acommunication partner, the transmitting-antenna control unit 16T setsand holds the beam pattern of the transmitting antenna ATX in thesetting period PH1.

When the retransmission-bit determining unit 15A determines that theretry bit in the retry field in a MAC frame is 1, that is, determinesthat an initial transmission or retransmission of the same MAC frame hasbeen previously performed, the transmitting-antenna control unit 16Tchanges the beam pattern of the transmitting antenna ATX which is to beused for a response with an Ack frame.

When the retransmission-bit determining unit 15A determines that theretry bit in the retry field in a MAC frame is 0, that is, determinesthat an initial transmission of a new MAC frame has been received, thetransmitting-antenna control unit 16T holds the beam pattern of thetransmitting antenna ATX which was set in the setting period PH1 andwhich is used for a response with an Ack frame.

When the response-needed/not-needed determining unit 12 determines thata response with an Ack frame is not needed, the transmitting-antennacontrol unit 16T holds the beam pattern of the transmitting antenna ATXwhich was set in the setting period PH1.

Before starting the period PH2 (see FIG. 18A) of communication with thecommunication partner, the receiving-antenna control unit 16R sets andholds the beam pattern of the receiving antenna ARX in the settingperiod PH1. Although details are described below, the receiving-antennacontrol unit 16R may also change or hold the beam pattern of thereceiving antenna ARX in accordance with a result of the determinationmade by the response-needed/not-needed determining unit 12, theretransmission-bit determining unit 15A, or the SN determining unit 15B.

Next, an operation procedure from when the wireless communication device1 in the present embodiment receives a MAC frame until it transmits anAck frame will be described with reference to FIG. 4A and FIG. 4B.

FIG. 4A is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna ATX for an Ackframe in response to a MAC frame (for example, a data frame) received bythe data-receiving wireless communication device Dv2 in the firstembodiment. FIG. 4B is a flowchart illustrating another example of theprocedure for setting the beam pattern of the transmitting antenna ATXfor an Ack frame in response to a MAC frame (for example, a data frame)received by the data-receiving wireless communication device Dv2 in thefirst embodiment.

A description in FIG. 4A will be given assuming that the wirelesscommunication device 1A (the data-receiving wireless communicationdevice Dv2) shown in FIG. 3A has properly received a MAC frame (forexample, a data frame), and a description in FIG. 4B will be givenassuming that the wireless communication device 1B (the data-receivingwireless communication device Dv2) shown in FIG. 3B has properlyreceived a MAC frame (for example, a data frame) (P1).

In FIG. 4A, the response-needed/not-needed determining unit 12determines whether or not a response with an Ack frame indicating properreception of the MAC frame is needed, on the basis of the frame type orresponse type of the MAC frame demodulated by the wireless receivingunit 11 (P2). The response-needed/not-needed determining unit 12 outputsa result of the determination to the response-frame generating unit 13,the retransmission-bit determining unit 15A, and thetransmitting-antenna control unit 16T.

When the response-needed/not-needed determining unit 12 determines thata response with an Ack frame is not needed (P2, NO), thetransmitting-antenna control unit 16T holds the beam pattern of thetransmitting antenna ATX (P3).

When the response-needed/not-needed determining unit 12 determines thata response with an Ack frame is needed (P2, YES), the response-framegenerating unit 13 generates an Ack frame indicating reception of theMAC frame and outputs the Ack frame to the wireless transmitting unit14.

When the response-needed/not-needed determining unit 12 determines thata response with an Ack frame is needed (P2, YES), the retransmission-bitdetermining unit 15A determines whether the retry bit in the retry fieldin the MAC frame demodulated by the wireless receiving unit 11 is 1indicating retransmission or 0 indicating new transmission (P4). Theretransmission-bit determining unit 15A outputs a result of thedetermination to the transmitting-antenna control unit 16T.

When the retransmission-bit determining unit 15A determines that theretry bit in the retry field in the MAC frame is 0 (P4, YES), thetransmitting-antenna control unit 16T holds the beam pattern of thetransmitting antenna ATX which is to be used for a response with an Ackframe (P5).

By using the beam pattern of the transmitting antenna ATX which was heldin step P5, the wireless transmitting unit 14 transmits an Ack framegenerated by the response-frame generating unit 13 to the communicationpartner (P6).

On the other hand, when the retransmission-bit determining unit 15Adetermines that the retry bit in the retry field in the MAC frame is 1(P4, NO), the transmitting-antenna control unit 16T changes the beampattern of the transmitting antenna ATX which is to be used for aresponse with an Ack frame (P7).

The wireless transmitting unit 14 uses the beam pattern of thetransmitting antenna ATX after the change in step P7 to transmit an Ackframe generated by the response-frame generating unit 13 to thecommunication partner (P8). The operation of the wireless communicationdevice 1A after step P3, step P6, or step P8 returns to step P1.

Next, an operation procedure from when the wireless communication device1B receives a MAC frame until it makes a response with an Ack frame willbe described with reference to FIG. 4B, in which descriptions foroperations that are the same as the operations shown in FIG. 4A areomitted or briefly given with the same step numbers given thereto, anddifferent details will be described.

In FIG. 4B, when the response-needed/not-needed determining unit 12determines that a response with an Ack frame is needed (P2, YES), the SNdetermining unit 15B determines whether or not a stored SN and thereceived SN are the same (P4A). Regardless of a result of thedetermination in step P4A, the SN determining unit 15B stores thereceived SN (P9, P10).

When the SN determining unit 15B determines that the stored SN and thereceived SN do not match each other, the transmitting-antenna controlunit 16T holds, after step P9, the beam pattern of the transmittingantenna ATX which is to be used for a response with an Ack frame (P5).

When the stored SN and the received SN do not match each other, thismeans that the wireless communication device 1B received a MAC framegiven a new sequence number. Accordingly, the wireless communicationdevice 1B determines that the beam pattern of the transmitting antennaATX which was used for the previous response with an Ack frame isappropriate and it is not necessary to change the beam pattern of thetransmitting antenna ATX.

On the other hand, when the SN determining unit 15B determines that thestored SN and the received SN match each other, the transmitting-antennacontrol unit 16T changes, after step P9, the beam pattern of thetransmitting antenna ATX which is to be used for a response with an Ackframe (P7).

When the stored SN and the received SN match each other, this means thatthe wireless communication device 1B received a MAC frame given the samesequence number. Accordingly, the wireless communication device 1Bdetermines that the beam pattern of the transmitting antenna ATX whichwas used for the previous response with an Ack frame is inappropriateand it is necessary to change the beam pattern of the transmittingantenna ATX.

Next, one example of signaling when the wireless communication devicesin the present embodiment directly perform wireless communication willbe described with reference to FIG. 5A, FIG. 5B, FIG. 6A, and FIG. 6B.In descriptions in FIG. 5B, FIG. 6A, and FIG. 6B, descriptions foroperations that are the same as the operations shown in FIG. 5A areomitted or briefly given with the same numerals given thereto, anddifferent details will be described.

FIG. 5A is a sequence diagram showing one example of signaling in whicha sequence number SN is changed upon reception of an Ack frame, thesignaling being performed by the data-transmitting wirelesscommunication device and the data-receiving wireless communicationdevice in the first embodiment. FIG. 5B is a sequence diagram showingone example of signaling in which a sequence number SN is changed uponreaching of the upper limit of the number of retransmissions, thesignaling being performed by the data-transmitting wirelesscommunication device and the data-receiving wireless communicationdevice in the first embodiment.

FIG. 6A is a sequence diagram showing another example of signaling inwhich a sequence number SN is changed upon reception of an Ack frame,the signaling being performed by the data-transmitting wirelesscommunication device and the data-receiving wireless communicationdevice in the first embodiment. FIG. 6B is a sequence diagram showinganother example of signaling in which a sequence number SN is changedupon reaching of the upper limit of the number of retransmissions, thesignaling being performed by the data-transmitting wirelesscommunication device and the data-receiving wireless communicationdevice in the first embodiment.

In the sequence diagrams below, a wireless communication device thattransmits data in the present embodiment is described as adata-transmitting wireless communication device Dv1, and a wirelesscommunication device that receives data in the present embodiment isdescribed as a data-receiving wireless communication device Dv2.

Also, FIG. 5A and FIG. 5B show operations of the data-transmittingwireless communication device Dv1 and the data-receiving wirelesscommunication device Dv2 having the configuration of the wirelesscommunication device 1A shown in FIG. 3A, and FIG. 6A and FIG. 6B showoperations of the data-transmitting wireless communication device Dv1and the data-receiving wireless communication device Dv2 having theconfiguration of the wireless communication device 1B shown in FIG. 3B.

In FIG. 5A, the data-transmitting wireless communication device Dv1transmits the MAC frame (for example, a data frame) “sequence number=1and retry bit=0” to the data-receiving wireless communication device Dv2(S1). The data-receiving wireless communication device Dv2 properlyreceives the MAC frame transmitted from the data-transmitting wirelesscommunication device Dv1 and uses the beam pattern (for example, PtA) ofthe transmitting antenna ATX to transmit an Ack frame to thedata-transmitting wireless communication device Dv1 (S1). However, instep S1, the Ack frame does not arrive at the data-transmitting wirelesscommunication device Dv1 (S1).

The data-transmitting wireless communication device Dv1 changes theretry bit from 0 to 1 and retransmits the data frame “sequence number=1and retry bit=1” (S2). The data-receiving wireless communication deviceDv2 properly receives the data frame retransmitted from thedata-transmitting wireless communication device Dv1, changes the beampattern of the transmitting antenna ATX, for example, from the beampattern PtA to a beam pattern PtB, and transmits an Ack frame to thedata-transmitting wireless communication device Dv1 (S2).

Since the Ack frame transmitted from the data-receiving wirelesscommunication device Dv2 in step S2 arrives at the data-transmittingwireless communication device Dv1, that is, is properly received by thedata-transmitting wireless communication device Dv1, thedata-transmitting wireless communication device Dv1 increments thesequence number by, for example, 1 (S3), generates a data frame“sequence number=2 and retry bit=0”, and transmits the data frame to thedata-receiving wireless communication device Dv2 (S4).

The data-receiving wireless communication device Dv2 properly receivesthe data frame transmitted from the data-transmitting wirelesscommunication device Dv1 in step S4 and uses the beam pattern PtB of thetransmitting antenna ATX after the change in step S2 to transmit an Ackframe to the data-transmitting wireless communication device Dv1 (S4).

The Ack frame transmitted in step S4 is properly received by thedata-transmitting wireless communication device Dv1, as long as thecommunication environment between the data-transmitting wirelesscommunication device Dv1 and the data-receiving wireless communicationdevice Dv2 and the beam patterns of the antennas are appropriate.

In FIG. 5B, the data-transmitting wireless communication device Dv1retransmits the data frame “sequence number=1 and retry bit=1” (S5). Thedata-receiving wireless communication device Dv2 properly receives thedata frame retransmitted from the data-transmitting wirelesscommunication device Dv1, changes the beam pattern of the transmittingantenna ATX, for example, from a beam pattern PtA to a beam pattern PtB,and transmits an Ack frame to the data-transmitting wirelesscommunication device Dv1 (S5). However, in step S5, the Ack frame doesnot arrive at the data-transmitting wireless communication device Dv1(S5).

In step S6, similarly, the data-receiving wireless communication deviceDv2 also changes the beam pattern of the transmitting antenna ATX, forexample, from the beam pattern PtB to a beam pattern PtC and transmitsan Ack frame to the data-transmitting wireless communication device Dv1(S6). However, in step S6, the Ack frame does not arrive at thedata-transmitting wireless communication device Dv1 (S6).

When the data-transmitting wireless communication device Dv1 determinesthat the number of retransmissions of the data frame reaches apredetermined upper limit of the number of retransmissions, thedata-transmitting wireless communication device Dv1 suspends theretransmission of the data frame “sequence number=1”, although the dataframe “sequence number=1” is properly received by the data-receivingwireless communication device Dv2 in practice, increments the sequencenumber by 1 to change the sequence number (S7), and transmits a dataframe “sequence number=2 and retry bit=0” to the data-receiving wirelesscommunication device Dv2 (S8).

The data-receiving wireless communication device Dv2 properly receivesthe data frame “sequence number=2 and retry bit=0” transmitted from thedata-transmitting wireless communication device Dv1 and uses, forexample, the beam pattern PtC set in step S6 as the beam pattern of thetransmitting antenna ATX to transmit an Ack frame to thedata-transmitting wireless communication device Dv1 (S8). However, instep Sb, the Ack frame does not arrive at the data-transmitting wirelesscommunication device Dv1 (S8).

In step S8, the data-receiving wireless communication device Dv2 uses,as the beam pattern of the transmitting antenna ATX, the same beampattern PtC as that in step S6 to transmit the Ack frame. That is, sincethe determination in step S7 made by the data-transmitting wirelesscommunication device Dv1 is unknown to the data-receiving wirelesscommunication device Dv2, it is difficult for the data-receivingwireless communication device Dv2 to make the determination in step S8as to whether the change of the sequence number to 2 is caused by thearrival of the Ack frame or by the reaching of the upper limit of thenumber of retransmissions in step S7.

Thus, the data-receiving wireless communication device Dv2 uses, in stepS8, the procedure to re-check whether or not the transmission with thebeam pattern PtC arrives, by using the same beam pattern as that in stepS6 as the beam pattern used for transmitting the Ack frame. With thisprocedure, in step S8, it is possible to reduce unnecessary periods dueto checking with all beam patterns.

The data-transmitting wireless communication device Dv1 changes theretry bit from 0 to 1 and retransmits the data frame “sequence number=2and retry bit=1” (S9). The data-receiving wireless communication deviceDv2 properly receives the data frame retransmitted from thedata-transmitting wireless communication device Dv1, changes the beampattern of the transmitting antenna ATX, for example, from the beampattern PtC to a beam pattern PtD, and transmits an Ack frame to thedata-transmitting wireless communication device Dv1 (S9). The Ack frametransmitted in step S9 is properly received by the data-transmittingwireless communication device Dv1, as long as the communicationenvironment between the data-transmitting wireless communication deviceDv1 and the data-receiving wireless communication device Dv2 and thebeam patterns of the antennas are appropriate.

In the sequence diagrams in FIG. 6A and FIG. 6B, the method for thedata-receiving wireless communication device Dv2 to determine whether ornot the same data frame has been retransmitted is different from that inthe sequence diagrams in FIG. 5A and FIG. 5B, the details other than thedetermination method are the same, and thus descriptions thereof areomitted.

That is, in FIG. 6A and FIG. 6B, when the data-receiving wirelesscommunication device Dv2 properly receives a data frame transmitted fromthe data-transmitting wireless communication device Dv1 and determinesthat a response with an Ack frame is needed, the data-receiving wirelesscommunication device Dv2 transmits an Ack frame by using the set beampattern of the transmitting antenna ATX, upon determining that thestored SN and the received SN are not the same.

Next, one example of the beam pattern of each antenna when the wirelesscommunication devices in the present embodiment directly performwireless communication will be described with reference to FIG. 7A, FIG.7B, FIG. 7C, FIG. 7D, FIG. 7E, and FIG. 7F.

FIG. 7A is an explanatory diagram showing an example in whichtransmission of a data frame from the data-transmitting wirelesscommunication device Dv1 to the data-receiving wireless communicationdevice Dv2 has succeeded after the beam pattern was determined. FIG. 7Bis an explanatory diagram showing an example in which transmission of anAck frame from the data-receiving wireless communication device Dv2 tothe data-transmitting wireless communication device Dv1 has succeededafter the beam pattern was determined.

FIG. 7C is an explanatory diagram showing an example in whichtransmission of a data frame from the data-transmitting wirelesscommunication device Dv1 to the data-receiving wireless communicationdevice Dv2 has succeeded after the data-receiving wireless communicationdevice Dv2 was rotated. FIG. 7D is an explanatory diagram showing anexample in which transmission of an Ack frame from the data-receivingwireless communication device Dv2 to the data-transmitting wirelesscommunication device Dv1 has failed after the data-receiving wirelesscommunication device Dv2 was rotated.

FIG. 7E is an explanatory diagram showing an example in whichtransmission of a data frame from the data-transmitting wirelesscommunication device Dv1 to the data-receiving wireless communicationdevice Dv2 has succeeded after the data-receiving wireless communicationdevice Dv2 was rotated. FIG. 7F is an explanatory diagram showing anexample in which transmission of an Ack frame from the data-receivingwireless communication device Dv2 to the data-transmitting wirelesscommunication device Dv1 has succeeded after the data-receiving wirelesscommunication device Dv2 was rotated and the beam pattern of thetransmitting antenna ATX was changed.

In FIG. 7A, FIG. 7C, and FIG. 7E, the beam pattern of the transmittingantenna ATX of the data-transmitting wireless communication device Dv1is denoted by a thick solid line, and the beam pattern of the receivingantenna ARX of the data-receiving wireless communication device Dv2 isdenoted by a thick dotted line. In FIG. 7B, FIG. 7D, and FIG. 7F, thebeam pattern of the receiving antenna ARX of the data-transmittingwireless communication device Dv1 is denoted by a thick dotted line, andthe beam pattern of the transmitting antenna ATX of the data-receivingwireless communication device Dv2 is denoted by a thick solid line.

In FIG. 7A and FIG. 7B, a combination of the beam pattern of thetransmitting antenna ATX of the data-transmitting wireless communicationdevice Dv1 and the beam pattern of the receiving antenna ARX of thedata-receiving wireless communication device Dv2 has an overlappingportion. Thus, in FIG. 7A, a data frame transmitted by thedata-transmitting wireless communication device Dv1 is received by thedata-receiving wireless communication device Dv2. Also, in FIG. 7B, acombination of the beam pattern of the receiving antenna ARX of thedata-transmitting wireless communication device Dv1 and the beam patternof the transmitting antenna ATX of the data-receiving wirelesscommunication device Dv2 has an overlapping portion. Thus, an Ack frametransmitted by the data-receiving wireless communication device Dv2 isreceived by the data-transmitting wireless communication device Dv1.

In FIG. 7C, since the data-receiving wireless communication device Dv2was rotated, the overlapping state of the beam pattern of the receivingantenna ARX of the data-receiving wireless communication device Dv2 andthe beam pattern of the transmitting antenna ATX changes. In FIG. 7C, acombination of the beam pattern of the transmitting antenna ATX of thedata-transmitting wireless communication device Dv1 and the beam patternof the receiving antenna ARX of the data-receiving wirelesscommunication device Dv2 has an overlapping portion. Thus, a data frametransmitted by the data-transmitting wireless communication device Dv1is received by the data-receiving wireless communication device Dv2.

However, in FIG. 7D, the combination of the beam pattern of thereceiving antenna ARX of the data-transmitting wireless communicationdevice Dv1 and the beam pattern of the transmitting antenna ATX of thedata-receiving wireless communication device Dv2 has no overlapping.Thus, an Ack frame transmitted by the data-receiving wirelesscommunication device Dv2 is not received by the data-transmittingwireless communication device Dv1, and the data-receiving wirelesscommunication device Dv2 changes the beam pattern of the transmittingantenna ATX which is to be used for transmitting the Ack frame.

Descriptions in FIG. 7E and FIG. 7F are given of states in which thedata-receiving wireless communication device Dv2 was rotated, as in FIG.7C and FIG. 7D. In FIG. 7E, the combination of the beam pattern of thetransmitting antenna ATX of the data-transmitting wireless communicationdevice Dv1 and the beam pattern of the receiving antenna ARX of thedata-receiving wireless communication device Dv2 has an overlappingportion. A data frame transmitted by the data-transmitting wirelesscommunication device Dv1 is received by the data-receiving wirelesscommunication device Dv2.

In FIG. 7F, since the beam pattern in FIG. 7D has been changed, thecombination of the beam pattern of the receiving antenna ARX of thedata-transmitting wireless communication device Dv1 and the beam patternof the transmitting antenna ATX of the data-receiving wirelesscommunication device Dv2 has an overlapping portion. Thus, when thedata-receiving wireless communication device Dv2 transmits an Ack frameby using the changed beam pattern of the transmitting antenna ATX, theAck frame transmitted by the data-receiving wireless communicationdevice Dv2 is received by the data-transmitting wireless communicationdevice Dv1.

As described above, the wireless communication device 1 in the presentembodiment properly receives a MAC frame (for example, a data frame)transmitted from a communication partner, and upon determining that aresponse with an Ack frame indicating a response to the MAC frame isneeded, the wireless communication device 1 determines whether or notthe same MAC frame is retransmitted from the communication partner, inaccordance with the contents of the retry bit in the MAC frame orthrough comparison of the stored SN with the received SN.

When the wireless communication device 1 determines that the same MACframe is retransmitted from the communication partner, it determinesthat the beam pattern of the transmitting antenna ATX which was used fortransmitting the previously transmitted Ack frame was not appropriate,and changes the beam pattern of the transmitting antenna ATX. Thewireless communication device 1 uses the changed beam pattern totransmit an Ack frame.

Thus, the wireless communication device 1 does not change the beampattern of the transmitting antenna ATX which is to be used fortransmitting the Ack frame, when the same MAC frame is not retransmittedfrom the communication partner, and changes the beam pattern of thetransmitting antenna ATX, when the same MAC frame is retransmitted.Thus, it is possible to avoid an unnecessary change of the beam patternof the transmitting antenna ATX. Accordingly, since the wirelesscommunication device 1 can quickly restore a communication channel, itis possible to suppress deterioration of the environment ofcommunication (the quality of communication) with a communicationpartner. That is, since the wireless communication device 1 can reducean unnecessary occupancy time in a communication band, it is possible toimprove the effective throughput and it is possible to further reducethe power consumption and the time taken for connection to acommunication partner.

Also, in the present embodiment, the wireless communication device 1 candetermine whether or not the same MAC frame is retransmitted from thecommunication partner, on the basis of the sequence numbers of MACframes, and thus supports, for example, MAC frames having formats thatdo not include retry bits, making it possible to determine whether ornot a MAC frame is retransmitted. When the wireless communication device1 receives, a plurality of times or more in a certain amount of time, aMAC frame having the same transmission-source address and indicatingthat it is retransmitted, the wireless communication device 1 maydetermine that a previously transmitted Ack frame has not arrived.

Also, for example, in the communication period PH2 after a predeterminedcertain period has passed from the completion of the setting period PH1shown in FIG. 18A, even when the retry bit in a MAC frame transmittedfrom the communication partner is 0, the wireless communication device 1may change the beam pattern of the transmitting antenna ATX which is tobe used for transmitting an Ack frame.

For example, in the communication period PH2 after a predeterminedcertain period has passed from the completion of the setting period PH1shown in FIG. 18A, there are cases in which the communicationenvironment has deteriorated compared with the communication environmentat the time of start of the communication period PH2. Accordingly, bychanging the beam pattern of the transmitting antenna ATX which is to beused for transmitting an Ack frame, the wireless communication device 1can quickly restore a communication channel with a communicationpartner.

The predetermined certain period is, for example, the time with whichthe wireless communication device 1 increments the sequence number of aMAC frame by 1. This allows the wireless communication device 1 toaccurately distinguish between the quick increment processing for thesequence number upon arrival of an Ack frame at the communicationpartner and the increment processing for the sequence number when acertain time has passed after a MAC frame is retransmitted because ofnon-arrival of an Ack frame. Thus, the wireless communication device 1can make a high-accuracy determination as to retransmission of the sameMAC frame and can further appropriately change the beam pattern of thetransmitting antenna ATX.

Next, in the present embodiment, when the retry bit in a MAC frame (forexample, a data frame) received from the communication partner to thewireless communication device 1 is 0 or when the sequence number thereofchanges, it is thought that the beam pattern of the transmitting antennaATX that the wireless communication device 1 used to transmit an Ackframe was appropriate during the transmission of the Ack frame.

Accordingly, when the wireless communication device 1 transmits a MACframe (for example, a data frame) after transmitting an Ack frame, itmay also use the beam pattern of the transmitting antenna ATX which wasused for transmitting the Ack frame (see FIG. 8A and FIG. 8B). Althoughthe time from the transmission of an Ack frame to the transmission of aMAC frame (for example, a data frame) also depends on the communicationenvironment, it is estimated to be roughly about tens of microseconds totens of milliseconds, which is a sufficiently short period, comparedwith the setting period PH1 (for example, tens of milliseconds tohundreds of milliseconds) shown in FIG. 18A.

FIG. 8A is a flowchart illustrating one example of an operationprocedure for the data-receiving wireless communication device Dv2 inthe first embodiment to transmit a data frame by using the beam patternof the transmitting antenna ATX for transmitting an Ack frame. FIG. 8Bis a sequence diagram showing one example of signaling for thedata-receiving wireless communication device Dv2 shown in FIG. 8A totransmit a data frame by using the beam pattern of the transmittingantenna ATX for transmitting an Ack frame. In FIG. 8A, descriptions foroperations that are the same as the operations shown in FIG. 4B areomitted or briefly given with the same numerals given thereto, anddifferent details will be described.

In FIG. 8A, after step P6, the wireless transmitting unit 14 uses thebeam pattern of the transmitting antenna ATX, the beam pattern beingheld in step P5, to transmit a MAC frame (for example, a data frame) tothe communication partner (P11).

In FIG. 8B, after step S4, the data-receiving wireless communicationdevice Dv2 uses the beam pattern of the transmitting antenna ATX, thebeam pattern being used in step S4, to transmit a MAC frame (forexample, a data frame) to the data-transmitting wireless communicationdevice Dv1 (S10).

Since this allows the wireless communication device 1 (thedata-receiving wireless communication device Dv2) to substantially set,during response with an Ack frame indicating reception of a MAC frametransmitted from the communication partner, the beam pattern of thetransmitting antenna ATX for transmitting a data frame, it is possibleto omit the setting period PH1 for the data-receiving wirelesscommunication device Dv2 to transmit a MAC frame. Also, since theprocedure and the time involved in setting the setting period PH1 can beomitted, the effective throughput can be improved.

Modification 1 of First Embodiment

In the first embodiment, in the data-receiving wireless communicationdevice Dv2, for example, no distinction is made as to whether the causefor why the retry bit of a MAC frame has changed from 1 to 0 or thesequence number has changed is that the data-transmitting wirelesscommunication device Dv1 has properly received an Ack frame or thenumber of retransmissions of a MAC frame retransmitted by thedata-transmitting wireless communication device Dv1 has reached thepredetermined upper limit of the number of retransmissions.

In a first modification (hereinafter referred to as “present firstmodification”) in the first embodiment, upon determining that the causecorresponds to one of the following four cases, the data-receivingwireless communication device Dv2 determines that, for example, thecause for why the retry bit of the MAC frame has changed from 1 to 0 orthe sequence number has changed is that the number of retransmissions ofa MAC frame has reached the predetermined upper limit number of times.That is, the data-receiving wireless communication device Dv2 changesthe beam pattern of the transmitting antenna ATX which is to be used fortransmitting an Ack frame, without holding the beam pattern (see FIG.9).

In a first case, the data-receiving wireless communication device Dv2counts the number of receptions of the retransmitted same MAC frame,until receiving, from the data-transmitting wireless communicationdevice Dv1, a notification indicating that the number of retransmissionshas reached the predetermined upper limit number of times. When thecounted number of receptions and the upper limit number of times of theretransmission match each other, and further, for example, the retry bitin the MAC frame changes from 1 to 0 or the sequence number changes, thedata-receiving wireless communication device Dv2 determines that thecause is that the number of retransmissions of the MAC frame has reachedthe predetermined upper limit number of times.

In a second case, the data-receiving wireless communication device Dv2acquires information of the number of retransmissions, the informationbeing included in a MAC frame transmitted from the data-transmittingwireless communication device Dv1, until receiving, from thedata-transmitting wireless communication device Dv1, a notificationindicating that the number of retransmissions has reached thepredetermined upper limit number of times. When the acquired number ofretransmissions and the upper limit number of times of theretransmission match each other, and further, for example, the retry bitin the MAC frame changes from 1 to 0 or the sequence number changes, thedata-receiving wireless communication device Dv2 determines that thecause is that the number of retransmissions of the MAC frame has reachedthe predetermined upper limit number of times.

In a third case, the data-receiving wireless communication device Dv2acquires information of the number of remaining retransmittable times,the information being included in a MAC frame transmitted from thedata-transmitting wireless communication device Dv1. When the acquirednumber of remaining retransmittable times reaches 0, and further, forexample, the retry bit in the MAC frame changes from 1 to 0 or thesequence number changes, the data-receiving wireless communicationdevice Dv2 determines that the cause is that the number ofretransmissions of the MAC frame has reached the predetermined upperlimit number of times.

In a fourth case, when the data-receiving wireless communication deviceDv2 detects a flag indicating a last retransmission from a MAC frametransmitted from the data-transmitting wireless communication deviceDv1, and further, for example, when the retry bit in the MAC framechanges from 1 to 0 or the sequence number changes, the data-receivingwireless communication device Dv2 determines that the cause is that thenumber of retransmissions of the MAC frame has reached the predeterminedupper limit number of times.

FIG. 9 is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna ATX for an Ackframe in response to a data frame received by the data-receivingwireless communication device Dv2 in the first modification of the firstembodiment. In FIG. 9, descriptions for operations that are the same asthe operations shown in FIG. 8A are omitted or briefly given with thesame numerals given thereto, and different details will be described.

In FIG. 9, on the basis of the first to fourth cases described above,the SN determining unit 15B determines that the cause for why thesequence number of the MAC frame (for example, a data frame) received instep P1 has changed is that the number of retransmissions of the MACframe has reached the predetermined upper limit number of times (P12).

When the SN determining unit 15B determines that the cause for why thesequence number of the MAC frame (for example, a data frame) has changedcorresponds to one of the first case to the fourth case described above,the transmitting-antenna control unit 16T determines whether or not thenumber of retransmissions of the MAC frame has reached the predeterminedupper limit number of times. Upon determining that the number ofretransmissions of the MAC frame has reached the upper limit number oftimes (P12, YES), the transmitting-antenna control unit 16T changes thebeam pattern of the transmitting antenna ATX which is to be used for aresponse with an Ack frame (P7).

By using the beam pattern of the transmitting antenna ATX after thechange in step P7, the wireless transmitting unit 14 transmits an Ackframe generated by the response-frame generating unit 13 to thecommunication partner (P8).

On the other hand, when the SN determining unit 15B determines that thecause for why the sequence number of the MAC frame (for example, a dataframe) has changed is not that the number of retransmissions of the MACframe has reached the predetermined upper limit number of times of theretransmission (P12, NO), the transmitting-antenna control unit 16Tholds the beam pattern of the transmitting antenna ATX which is to beused for a response with an Ack frame (P5).

The wireless transmitting unit 14 uses the beam pattern of thetransmitting antenna ATX, the beam pattern being held in step P5, totransmit an Ack frame generated by the response-frame generating unit 13to the communication partner (the data-transmitting wirelesscommunication device Dv1) (P6), and the data-receiving wirelesscommunication device Dv2 uses the beam pattern of the transmittingantenna ATX, the beam pattern being held in step P5, to transmit a MACframe (for example, a data frame) to the communication partner (thedata-transmitting wireless communication device Dv1) (P11).

As described above, since the wireless communication device 1 in thepresent first modification is configured so that the data-receivingwireless communication device Dv2 determines the cause of change of thesequence number, it is possible to reduce the number of transmissions ofan Ack frame and it is possible to set the beam pattern of thetransmitting antenna ATX which is appropriate for transmitting an Ackframe to the communication partner.

Second Modification of First Embodiment

In the first embodiment, when the retry bit in a MAC frame (for example,a data frame) received from the communication partner (thedata-transmitting wireless communication device Dv1) to the wirelesscommunication device 1 (the data-receiving wireless communication deviceDv2) is 0 or the sequence number thereof changes, it is thought that thebeam pattern of the transmitting antenna ATX that the wirelesscommunication device 1 (the data-receiving wireless communication deviceDv2) used to transmit an Ack frame was appropriate at the time oftransmission of the Ack frame.

In a second modification (hereinafter referred to as “present secondmodification”) of the first embodiment, the data-receiving wirelesscommunication device Dv2 uses, as the beam pattern of the receivingantenna ARX, the same beam pattern as the beam pattern of thetransmitting antenna ATX used during transmission of an Ack frame (seeFIG. 10).

For example, during reception of a MAC frame, the data-transmittingwireless communication device Dv1 and the data-receiving wirelesscommunication device Dv2 set the beam pattern of the receiving antennaARX to the omnidirectional (omni) or quasi-omnidirectional (quasi-omni)beam pattern in many cases.

For example, in a TXOP (Transmission Opportunity) period in CSMA/CA, thedata-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 do not need to receivea MAC frame transmitted from a third station and thus do not have to setthe beam pattern of the receiving antenna ARX to the omnidirectional(omni) or quasi-omnidirectional (quasi-omni) beam pattern.

Also, in an SP (Service Period) period in SPCA communication, thedata-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 can identify thetransmission source of a MAC frame that is received and thus do not haveto set the beam pattern of the receiving antenna ARX to theomnidirectional (omni) or quasi-omnidirectional (quasi-omni) beampattern.

FIG. 10 is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna for transmitting anAck frame in response to a data frame received by the data-receivingwireless communication device Dv2 in the second modification of thefirst embodiment and the beam pattern of the receiving antenna forreceiving a data frame next time. In FIG. 10, descriptions foroperations that are the same as the operations shown in FIG. 8A areomitted or briefly given with the same numerals given thereto, anddifferent details will be described.

In FIG. 10, after step P6, the receiving-antenna control unit 16R in thedata-receiving wireless communication device Dv2 uses the same beampattern as the beam pattern of the transmitting antenna ATX as the beampattern of the receiving antenna ARX in order to receive a MAC frametransmitted from the communication partner (the data-transmittingwireless communication device Dv1) (P14).

As a result, it is sufficient when the wireless communication device 1(the data-receiving wireless communication device Dv2) in the presentsecond modification forms a main beam in a specific direction withoutsetting the beam pattern of the receiving antenna ARX to theomnidirectivity (omni) or quasi-omnidirectivity (quasi-omni), thusmaking it possible to effectively use the communication band and toreduce the power consumption.

In addition, in the setting period PH1 in the next transmission cycle TRafter holding or changing the beam pattern of the transmitting antennaATX which is to be used to transmit an Ack frame, the wirelesscommunication device 1 (the data-receiving wireless communication deviceDv2) in the present second modification can, for example, omit thesetting of the beam pattern of the receiving antenna ARX and can set thesame beam pattern as the beam pattern of the transmitting antenna ATX.

Thus, in the setting period PH1 in the next transmission cycle TR, thewireless communication device 1 in the present second modification cansuppress using a communication channel (a communication band) needed toset the beam pattern of the receiving antenna ARX, thus making itpossible to effectively use the communication band and to reduce thepower consumption.

SECOND EMBODIMENT

In the second embodiment, a description will be given of a case inwhich, for example, the data-transmitting wireless communication deviceDv1 transmits the aggregation frame shown in FIG. 16A and thedata-receiving wireless communication device Dv2 makes a response with ablock Ack frame indicating that some or all MAC frames (MPDU) of theaggregation frame are received. The data-transmitting wirelesscommunication device Dv1 and the data-receiving wireless communicationdevice Dv2 in the present embodiment have configurations that aresimilar to that of the wireless communication device 1A shown in FIG. 3Aor the wireless communication device 1B shown in FIG. 3B.

First, an overview of an operation of direct wireless communicationbetween the data-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 in the presentembodiment will be described with reference to FIG. 11. FIG. 11 is asequence diagram showing one example of signaling regarding transmissionof an aggregation data frame, the signaling being performed by thedata-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 in the secondembodiment.

In FIG. 11A, the data-transmitting wireless communication device Dv1transmits an aggregation frame including a plurality of MAC frames(MPDU) to the data-receiving wireless communication device Dv2 (S21).The aggregation frame has a structure in which, for example, a MAC frame“sequence number=1”, a MAC frame “sequence number=2”, and a MAC frame“sequence number=3” are coupled.

When the data-receiving wireless communication device Dv2 properlyreceives the aggregation frame transmitted from the data-transmittingwireless communication device Dv1 and further determines that a responsewith a block Ack frame is needed, the data-receiving wirelesscommunication device Dv2 uses the beam pattern (for example, Pt2) of thetransmitting antenna ATX to transmit a block Ack frame to thedata-transmitting wireless communication device Dv1 (S21). However, inFIG. 11, the block Ack frame does not arrive at the data-transmittingwireless communication device Dv1 (S21).

Since the data-transmitting wireless communication device Dv1 does notreceive a block Ack frame corresponding to the aggregation frametransmitted in step S21, the data-transmitting wireless communicationdevice Dv1 retransmits the same aggregation frame as the aggregationframe transmitted in step S21 (S22).

Since the data-receiving wireless communication device Dv2 properlyreceives the aggregation frame retransmitted from the data-transmittingwireless communication device Dv1, the aggregation frame having the samesequence numbers, and further determines that a response with a blockAck frame is needed, the data-receiving wireless communication deviceDv2 changes the beam pattern (for example, Pt2) of the transmittingantenna ATX (S22). That is, upon determining that an initialtransmission or retransmission of an aggregation frame including MACframes (MPDU) that all have the same sequence numbers has beenpreviously performed, the data-receiving wireless communication deviceDv2 assumes that the beam pattern of the transmitting antenna ATX is notappropriate and changes the beam pattern of the transmitting antenna ATXwhich is to be used for a response with a block Ack frame.

Accordingly, the data-receiving wireless communication device Dv2 usesthe beam pattern (for example, Pt1) of the transmitting antenna ATXafter the change to transmit a block Ack frame to the data-transmittingwireless communication device Dv1 (S22). In FIG. 11, the block Ack frametransmitted in step S22 is properly received by the data-transmittingwireless communication device Dv1, since the communication environmentbetween the data-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 and the beam patternsof the antennas are appropriate.

Upon determining that an initial transmission or retransmission of anaggregation frame including MAC frames (MPDU) that all have the samesequence numbers has not been performed, that is, some MAC frames (MPDU)of the aggregation frame are newly transmitted, the data-receivingwireless communication device Dv2 holds the beam pattern of thetransmitting antenna ATX which is to be used for a response with a blockAck frame, without changing the beam pattern.

Next, an operation procedure from when the wireless communication device1 in the present embodiment receives an aggregation frame until ittransmits a block Ack frame will be described with reference to FIG. 12.FIG. 12 is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna for transmitting ablock Ack frame corresponding to an aggregation data frame received bythe data-receiving wireless communication device Dv2 in the secondembodiment.

In FIG. 12, a description will be given assuming that the wirelesscommunication device 1B shown in FIG. 3B has properly received at leastone MAC frame (MPDU) of an aggregation frame (P21).

In FIG. 12, the wireless receiving unit 11 determines whether or not allMAC frames (MPDU) of the properly received aggregation frame have beenproperly received (P22). When it is determined that all MAC frames(MPDU) have been properly received (P22, YES), theresponse-needed/not-needed determining unit 12 determines whether or nota response with a block Ack frame indicating the reception of theaggregation frame is needed, on the basis of the frame type or responsetype of each MPDU of the aggregation frame demodulated by the wirelessreceiving unit 11 (P23). The response-needed/not-needed determining unit12 outputs a result of the determination to the response-framegenerating unit 13, the SN determining unit 15B, and thetransmitting-antenna control unit 16T.

When the response-needed/not-needed determining unit 12 determines thata response with a block Ack frame is not needed (P23, NO), thetransmitting-antenna control unit 16T holds the beam pattern of thetransmitting antenna ATX (P24).

When the response-needed/not-needed determining unit 12 determines thata response with a block Ack frame is needed (P23, YES), theresponse-frame generating unit 13 generates a block Ack frame indicatingreception of an aggregation frame and outputs the block Ack frame to thewireless transmitting unit 14.

When the response-needed/not-needed determining unit 12 determines thata response with a block Ack frame is needed (P23, YES), the SNdetermining unit 15B determines whether or not a stored SN pattern and areceived SN pattern are the same (P25). The SN determining unit 15Bstores the received SN pattern, regardless of a result of thedetermination in step P25 (P26, P29).

For ease of description of the present embodiment, a set (pattern) ofthe sequence numbers of properly received MAC frames (MPDU) of apreviously received aggregation frame, the sequence numbers being storedby the SN determining unit 15B, is simply referred to as a “stored SNpattern”, and a set (pattern) of the sequence numbers of properlyreceived MAC frames (MPDU) of an aggregation frame received by thereceiving antenna ARX this time is simply referred to as a “received SNpattern”.

Since the SN determining unit 15B determines that the stored SN patternand the received SN pattern do not match each other, after step P26, thetransmitting-antenna control unit 16T holds the beam pattern of thetransmitting antenna ATX which is to be used for a response with a blockAck frame (P27).

When the stored SN pattern and the received SN pattern do not match eachother, this means that the wireless communication device 1B received anaggregation frame including a MAC frame (MPDU) given a new sequencenumber. Accordingly, it is thought that the beam pattern of thetransmitting antenna ATX which was used for the previous response with ablock Ack frame is appropriate and it is not necessary to change thebeam pattern of the transmitting antenna ATX.

The wireless transmitting unit 14 uses the beam pattern of thetransmitting antenna ATX, the beam pattern being held in step P27, totransmit a block Ack frame generated by the response-frame generatingunit 13 to the communication partner (the data-transmitting wirelesscommunication device Dv1) (P28).

On the other hand, since the SN determining unit 15B determines that thestored SN pattern and the received SN pattern match each other, afterstep P29, the transmitting-antenna control unit 16T changes the beampattern of the transmitting antenna ATX which is to be used for aresponse with a block Ack frame (P30).

When the stored SN pattern and the received SN pattern match each other,this means that an aggregation frame including a MAC frame (MPDU) giventhe same sequence number was retransmitted and the wirelesscommunication device 1B received the retransmitted aggregation frame.Accordingly, it is thought that the beam pattern of the transmittingantenna ATX which was used for the previous response with a block Ackframe is inappropriate and it is necessary to change the beam pattern ofthe transmitting antenna ATX.

The wireless transmitting unit 14 uses the beam pattern of thetransmitting antenna ATX after the change in step P30 to transmit ablock Ack frame generated by the response-frame generating unit 13 tothe communication partner (the data-transmitting wireless communicationdevice Dv1) (P31).

Also, when the wireless receiving unit 11 determines that all MAC frames(MPDU) have not been properly received (P22, NO), theresponse-needed/not-needed determining unit 12 determines whether or nota response with an block Ack frame indicating the reception of anaggregation frame is needed, on the basis of the frame type or responsetype of the aggregation frame demodulated by the wireless receiving unit11, that is, some properly received MAC frames (MPDU) thereof (P32). Theresponse-needed/not-needed determining unit 12 outputs a result of thedetermination to the response-frame generating unit 13, the SNdetermining unit 15B, and the transmitting-antenna control unit 16T.

When the response-needed/not-needed determining unit 12 determines thata response with a block Ack frame is not needed (P32, NO), thetransmitting-antenna control unit 16T holds the beam pattern of thetransmitting antenna ATX (P33).

When the response-needed/not-needed determining unit 12 determines thata response with a block Ack frame is needed (P32, YES), theresponse-frame generating unit 13 generates a block Ack frame indicatingthe reception of the aggregation frame and outputs the Ack frame to thewireless transmitting unit 14.

When the response-needed/not-needed determining unit 12 determines thata response with a block Ack frame is needed (P32, YES), the SNdetermining unit 15B determines that a stored SN pattern and a receivedSN pattern of some properly received MAC frames (MPDU) of theaggregation frame are the same (P34). The SN determining unit 15B storesthe received SN pattern, regardless of a result of the determination instep P34 (P35, P38).

Since the SN determining unit 15B determines that the stored SN patternand the received SN pattern of some properly received MAC frames (MPDU)of the aggregation frame do not match each other, after step P35, thetransmitting-antenna control unit 16T holds the beam pattern of thetransmitting antenna ATX which is to be used for a response with a blockAck frame (P36).

Since the stored SN pattern and the received SN pattern of some properlyreceived MAC frames (MPDU) of the aggregation frame do not match eachother, this means that the wireless communication device 1B received anaggregation frame including a MAC frame (MPDU) given a new sequencenumber. Accordingly, it is thought that the beam pattern of thetransmitting antenna ATX which was used for the previous response with ablock Ack frame is appropriate and it is not necessary to change thebeam pattern of the transmitting antenna ATX.

The wireless transmitting unit 14 uses the beam pattern of thetransmitting antenna ATX, the beam pattern being held in step P36, totransmit a block Ack frame generated by the response-frame generatingunit 13 to the communication partner (P37).

On the other hand, since the SN determining unit 15B determines that thestored SN pattern and the received SN pattern of some properly receivedMAC frames (MPDU) of the aggregation frame match each other, after stepP38, the transmitting-antenna control unit 16T changes the beam patternof the transmitting antenna ATX which is to be used for a response witha block Ack frame (P39).

Since the stored SN pattern and the received SN pattern of some properlyreceived MAC frames (MPDU) of the aggregation frame match each other,this means that an aggregation including a MAC frame (MPDU) given thesame sequence number was retransmitted and the wireless communicationdevice 1B received the retransmitted aggregation frame. Accordingly, itis thought that the beam pattern of the transmitting antenna ATX whichwas used for the previous response with a block Ack frame isinappropriate and it is necessary to change the beam pattern of thetransmitting antenna ATX.

The wireless transmitting unit 14 uses the beam pattern of thetransmitting antenna ATX after the change in step P39 to transmit ablock Ack frame generated by the response-frame generating unit 13 tothe communication partner (P40).

The operation of the wireless communication device 1A after step P28,step P31, step P37, or step P40 returns to step P21.

As described above, when the wireless communication device 1 in thepresent embodiment properly receives some or all MAC frames (MPDU) of anaggregation frame transmitted from the communication partner anddetermines that a response with a block Ack frame indicating a responseto the aggregation frame is needed, the wireless communication device 1compares a stored SN pattern with the received SN pattern to determinewhether or not the same aggregation frame was retransmitted from thecommunication partner.

Upon determining that the same aggregation frame was retransmitted fromthe communication partner, the wireless communication device 1 assumesthat the beam pattern of the transmitting antenna ATX used to transmitthe previously transmitted block Ack frame was not appropriate andchanges the beam pattern of the transmitting antenna ATX. The wirelesscommunication device 1 uses the changed beam pattern to transmit a blockAck frame.

Thus, when the same aggregation frame is not retransmitted from thecommunication partner, the wireless communication device 1 does notchange the beam pattern of the transmitting antenna ATX which is to beused for transmitting a block Ack frame, and changes the beam pattern ofthe transmitting antenna ATX when the same aggregation frame isretransmitted, thus making it possible to avoid an unnecessary change ofthe beam pattern of the transmitting antenna ATX.

Accordingly, by avoiding an unnecessary change of the beam pattern ofthe transmitting antenna ATX, the wireless communication device 1 canomit the setting period PH1 and a preparation period for setting thesetting period PH1, thus making it possible to quickly restore thecommunication channel and making it possible to suppress deteriorationof the environment of communication (the quality of communication) withthe communication partner. That is, the wireless communication device 1can reduce an unnecessary occupancy time (for example, the settingperiod PH1 and a preparation period for setting the setting period PH1)in a communication band, thus making it possible to improve theeffective throughput and further making it possible to reduce the powerconsumption and the time taken for connection to the communicationpartner.

In the present embodiment, all of the MAC frames (MPDU) of anaggregation frame are not necessarily always received, and, for example,when three MAC frames are coupled, a total of eight combinations ofreceptions are possible. Thus, in step P21 shown in FIG. 12, uponreceiving MAC frames that are included in an aggregation frame and thatare more than or equal to a predetermined threshold, the wirelesscommunication device 1B may determine that an aggregation frameincluding some MAC frames is received.

Accordingly, when the wireless communication device 1B receives MACframes that are included in an aggregation frame and that are fewer thanthe predetermined threshold and does not receive other frames, thewireless communication device 1B determines that no aggregation framehas been received, presuming that comparison of a stored SN pattern withthe received SN pattern becomes difficult. Thus, after properlyreceiving an aggregation frame, the wireless communication device 1B cancompare the stored SN pattern with the received SN pattern with highaccuracy, can avoid erroneous determination of retransmission of anaggregation frame, and can set the beam pattern of the antenna with highaccuracy.

Although various embodiments have been described above with reference tothe drawings, it goes without saying that the present disclosure is notlimited to such examples. It is apparent to those skilled in the artthat various variations or modifications can be conceived within thescope recited in the claims, and it is to be understood that suchvariations and modifications also naturally belong to the technicalscope of the present disclosure.

In each embodiment described above, although the wireless communicationdevice 1 transmits an Ack frame or block Ack frame by using the samefrequency as the frequency that the communication partner used totransmit a MAC frame (for example, a data frame), the wirelesscommunication device 1 may also transmit an Ack frame or block Ack frameby using a frequency that is different from the frequency that thecommunication partner used to transmit a MAC frame (for example, a dataframe).

In each embodiment described above, although the communication partnerof the wireless communication device 1 transmits a data frame by using adirectional band (for example, millimeter waves), the communicationpartner may transmit a data frame by using an un-directional band (forexample, microwaves).

Third Modification of First Embodiment

In the first or second embodiment, the situation of the communicationchannel between the data-transmitting wireless communication device Dv1and the data-receiving wireless communication device Dv2 can beaccurately determined using the retry bits, the sequence numbers, andthe sequence number pattern in an aggregation frame or MAC framesproperly received by the data-receiving wireless communication deviceDv2. For example, in a communication environment where the beam patternof the transmitting antenna ATX or the receiving antenna ARX is held, itis thought that the quality of communication between thedata-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 is high.

In a third modification of the first embodiment, the wirelesscommunication device 1 may reduce, for example, the transmit power (seeFIG. 13), may reduce the gain of the receiving antenna ARX, may increasethe MCS (Modulation and Coding Scheme: the degree of modulation) or thecoding rate, may increase the frame length of MAC frames, or mayincrease the number of coupled MAC frames in an aggregation frame. Thisallows the wireless communication device 1 to effectively use thewireless band and makes it possible to reduce the power consumption ofthe wireless communication device 1.

Also, for example, in a communication environment where the beam patternof the transmitting antenna ATX or the receiving antenna ARX is changed,it is thought that the quality of communication between thedata-transmitting wireless communication device Dv1 and thedata-receiving wireless communication device Dv2 deteriorates.

In the third modification of the first embodiment, the wirelesscommunication device 1 may increase, for example, the transmit power(see FIG. 13), may increase the gain of the receiving antenna ARX, mayreduce the MCS (Modulation and Coding Scheme: the degree of modulation),may reduce the frame length of MAC frames, may reduce the number ofcoupled MAC frames in an aggregation frame, or may change a carrierfrequency used to another carrier frequency.

For example, in accordance with deterioration of the quality ofcommunication, the wireless communication device 1 scans frequency bandsto thereby estimate a frequency band in which the quality ofcommunication is high. This allows the wireless communication device 1to avoid unnecessary retransmission of an aggregation frame or a MACframe, thus making it possible to effectively use the wireless band andmaking it possible to reduce the power consumption of the wirelesscommunication device 1.

FIG. 13 is a flowchart illustrating one example of a procedure forsetting the beam pattern of the transmitting antenna ATX fortransmitting an Ack frame corresponding to a MAC frame received by thedata-receiving wireless communication device Dv2 in the thirdmodification of the first embodiment. In FIG. 13, descriptions foroperations that are the same as the operations shown in FIG. 4A areomitted or briefly given with the same numerals given thereto, anddifferent details will be described.

In FIG. 13, after step P5, the wireless transmitting unit 14 reduces thetransmit power for an Ack frame generated by the response-framegenerating unit 13 (P15) and uses the beam pattern of the transmittingantenna ATX, the beam pattern being held in step P5, to transmit the Ackframe to the communication partner (P6).

Also, after step P7, the wireless transmitting unit 14 increases thetransmit power for an Ack frame generated by the response-framegenerating unit 13 (P16) and uses the beam pattern of the transmittingantenna ATX after the change in step P7 to transmit the Ack frame to thecommunication partner (P8).

Fourth Modification of First Embodiment

Although the transmission of a MAC frame, the transmission of a responsewith an Ack frame, the transmission of an aggregation frame, and thetransmission of a response with a block Ack frame have been described byway of example in each embodiment described above, the combination ofthe transmission and the response transmission may also be, for example,any of a combination of the transmission of RTS (Request To Send) andCTS (Clear To Send), a combination of SSW (Sector Sweep), SSW-FB (SectorSweep-Feedback), and SSW-Ack (Sector Sweep-Ack), a combination ofAssociation Request and Ack, and a combination of Association Responseand Ack.

FIG. 19A is a flowchart illustrating one example of a procedure forsetting the beam pattern of a transmitting antenna for a response frame(for example, a CTS frame) in response to a MAC frame (for example, anRTS frame) received by a data-receiving wireless communication device ina fourth modification of the first embodiment, and FIG. 19B is asequence diagram showing one example of signaling in which a frame typeis changed upon reception of a CTS frame, the signaling being performedby a data-transmitting wireless communication device and thedata-receiving wireless communication device in the fourth modificationof the first embodiment.

FIG. 19A has a flowchart and FIG. 19B has a sequence diagram when “data”and Ack” in FIG. 4A and FIG. 5A are replaced with “frame”.

Instead of checking whether or not the transmission of a response withan Ack frame is needed in P2 in FIG. 4A, whether or not the transmissionof a response with a frame is needed is checked in FIG. 19A. Instead ofchecking the retry bit in a data frame in P4 in FIG. 4A, whether or notthe type of previously received frame and the type of frame receivedthis time are different from each other is checked in FIG. 19A. That is,YES in P4R corresponds to a determination in S4R in FIG. 19B describedbelow, and NO in P4R corresponds to a determination in S2R in FIG. 19B.

Also, instead of transmitting a response with an Ack frame in P6 and P8in FIG. 4A, a response with a frame corresponding to the type ofreceived frame is transmitted in P6R and P8R in FIG. 19A. That is, P6Rcorresponds to the transmission of a response with an Ack frame in S4Rin FIG. 19, and P8R corresponds to the transmission of a response with aCTS frame in S2R in FIG. 19B.

Next, FIG. 19B is a sequence diagram of transmission and reception ofdata and Ack after transmission and reception of an RTS and a CTS. Sincethe RTS does not include a sequence number and a retry bit, thedata-receiving wireless communication device Dv2 does not make adetermination as to RTS retransmission. However, since thedata-receiving wireless communication device Dv2 has received a secondRTS, it changes the beam pattern in a second CTS transmission (S2R).That is, since this corresponds to NO in P4R in FIG. 19A, thedata-receiving wireless communication device Dv2 changes the beampattern.

Next, upon receiving the CTS, the data-transmitting wirelesscommunication device Dv1 changes the transmission frame type from “RTS”to “data” and transmits data including information of a sequence numberand a retry bit (S3R).

Next, since the data-receiving wireless communication device Dv2receives the data after transmitting the CTS, it determines that the CTSwas received by the data-transmitting wireless communication device Dv1and returns an Ack without changing the beam pattern (S4R). That is,since this corresponds to YES in P4R in FIG. 19A, the data-receivingwireless communication device Dv2 does not change the beam pattern.

Also, in the response transmission, not just in the case in which an Ackframe is transmitted, a Reverse Direction system for performingtransmission including a data frame and an Ack frame (for example asdescribed in IEEE802.11) may also be used.

In each embodiment described above, when the data-receiving wirelesscommunication device Dv2 changes the beam pattern of the transmittingantenna ATX, for example, it may set the beam pattern to one of a beampattern adjacent to the current beam pattern, a beam patterncorresponding to an identification number, which is given to each beampattern, and a randomly selected beam pattern among a plurality ofswitchable beam patterns.

In each embodiment described above, when a MAC frame or an aggregationframe is continuously received a plurality of times to exceed apredetermined threshold, the data-receiving wireless communicationdevice Dv2 may also change the beam pattern of the transmitting antennaATX. This allows the data-receiving wireless communication device Dv2 toavoid, for example, an unnecessary change of the beam pattern of thetransmitting antenna ATX, the change being caused by non-arrival of anAck frame or block Ack frame as a result of an instantaneous change inthe communication environment.

This application claims priority to Japanese Patent Application No.2013-126060, filed on Jun. 14, 2013, the contents of which are herebyincorporated by reference.

INDUSTRIAL APPLICABILITY

The present disclosure is useful as a wireless communication device thatavoids an unnecessary change of the beam pattern of an antenna and thatsuppresses deterioration of the quality of communication.

REFERENCE SIGNS LIST

-   -   1, 1A, 1B wireless communication device    -   11 wireless receiving unit    -   12 response-needed/not-needed determining unit    -   13 response-frame generating unit    -   14 wireless transmitting unit    -   16 antenna control unit    -   16R receiving-antenna control unit    -   16T transmitting-antenna control unit    -   15 determining unit    -   15A retransmission-bit determining unit    -   15B SN determining unit    -   ARX receiving antenna    -   ATX transmitting antenna    -   Dv1 data-transmitting wireless communication device    -   Dv2 data-receiving wireless communication device

The invention claimed is:
 1. A wireless communication device comprising:a receiver which, in operation, receives a first transmission frame viaa receiving antenna, the first transmission frame being a MAC frametransmitted from a communication partner; a controller which, inoperation, generates a first response frame indicating reception of thefirst transmission frame; determines whether or not the same firsttransmission frame is retransmitted from the communication partner; andupdates a beam pattern of a transmitting antenna in response todetermining the same first transmission frame is retransmitted from thecommunication partner; and a transmitter which, in operation, transmitsthe first response frame via the transmitting antenna using the updatedbeam pattern.
 2. The wireless communication device according to claim 1,wherein the first transmission frame includes retransmission bitinformation indicating whether or not the first transmission frame isretransmitted, and when the retransmission bit information in thereceived first transmission frame indicates retransmission of the firsttransmission frame, the controller determines that the same firsttransmission frame is retransmitted from the communication partner. 3.The wireless communication device according to claim 1, wherein thefirst transmission frame includes identification number informationindicating identification information of the first transmission frame,and when the identification number information in the received firsttransmission frame remains the same, the controller determines that thesame first transmission frame is retransmitted from the communicationpartner.
 4. The wireless communication device according to claim 1,wherein, after the first response frame is transmitted, the controllermaintains the beam pattern of the transmitting antenna in response toreceiving a second transmission frame transmitted from the communicationpartner, the second transmission frame being of a frame type differentfrom the first transmission frame, and the transmitter transmits a newtransmission frame to the communication partner using the maintainedbeam pattern of the transmitting antenna.
 5. The wireless communicationdevice according to claim 1, wherein, after the first response frame istransmitted, the controller determines whether or not the number ofretransmissions of the first transmission frame has reached apredetermined upper limit number of times in response to receiving asecond transmission frame transmitted from the communication partner,the second transmission frame being of a frame type different from thefirst transmission frame; and when the controller determines that thenumber of retransmissions of the first transmission frame has reachedthe predetermined upper limit number of times, the controller updatesthe beam pattern of the transmitting antenna for use in transmitting asecond response frame indicating reception of the second transmissionframe.
 6. The wireless communication device according to claim 1,wherein, after the first response frame is transmitted, the controllermaintains the beam pattern of the transmitting antenna and sets, for thereceiving antenna, a beam pattern that is the same as the maintainedbeam pattern of the transmitting antenna in response to receiving asecond transmission frame transmitted from the communication partner,the second transmission frame being different from the firsttransmission frame.
 7. The wireless communication device according toclaim 1, wherein the first transmission frame transmitted from thecommunication partner includes a plurality of data frames, which includeidentification number information different from each other; and thetransmitter transmits the first response frame, which indicatesreception of some or all of the plurality of data frames, to thecommunication partner.
 8. A wireless communication method comprising:receiving a first transmission frame via a receiving antenna, the firsttransmission frame being a MAC frame transmitted from a communicationpartner; generating a first response frame indicating reception of thefirst transmission frame; determining whether or not the same firsttransmission frame is retransmitted from the communication partner;updating a beam pattern of a transmitting antenna in response todetermining the same first transmission frame is retransmitted from thecommunication partner; and transmitting the first response frame via thetransmitting antenna using the updated beam pattern.
 9. The wirelesscommunication method according to claim 8, wherein the firsttransmission frame includes retransmission bit information indicatingwhether or not the first transmission frame is retransmitted, anddetermining the same first transmission frame is retransmitted from thecommunication partner when the retransmission bit information in thereceived first transmission frame indicates retransmission of the firsttransmission frame.
 10. The wireless communication method according toclaim 8, wherein the first transmission frame includes identificationnumber information indicating identification information of the firsttransmission frame, and determining the same first transmission frame isretransmitted from the communication partner when the identificationnumber information in the received first transmission frame remains thesame.
 11. The wireless communication method according to claim 8,comprising: after transmitting the first response frame, maintaining thebeam pattern of the transmitting antenna in response to receiving asecond transmission frame transmitted from the communication partner,the second transmission frame being of a frame type different from thefirst transmission frame, and transmitting a new transmission frame tothe communication partner using the maintained beam pattern of thetransmitting antenna.
 12. The wireless communication method according toclaim 8, comprising: after transmitting the first response frame,determining whether or not the number of retransmissions of the firsttransmission frame has reached a predetermined upper limit number oftimes in response to receiving a second transmission frame transmittedfrom the communication partner, the second transmission frame being of aframe type different from the first transmission frame; and in responseto determining that the number of retransmissions of the firsttransmission frame has reached the predetermined upper limit number oftimes, updating the beam pattern of the transmitting antenna for use intransmitting a second response frame indicating reception of the secondtransmission frame.
 13. The wireless communication method according toclaim 8, comprising after transmitting the first response frame,maintaining the beam pattern of the transmitting antenna and setting,for the receiving antenna, a beam pattern that is the same as themaintained beam pattern of the transmitting antenna in response toreceiving a second transmission frame transmitted from the communicationpartner, the second transmission frame being different from the firsttransmission frame.
 14. The wireless communication method according toclaim 8, wherein the first transmission frame transmitted from thecommunication partner includes a plurality of data frames, which includeidentification number information different from each other; and thefirst response frame indicates reception of some or all of the pluralityof data frames.